So Ive spent a fair amount of time mapping this league mostly to expand my knowledge and test a few techniques as far as profitability and optimal strategies. A lot of this information is hard to come by spread across the internet in different forum posts or just plainly not there. So i decided to create a rough guide based on my findings of looking at the information that is out there and testing things myself. Things change from league to league drop rates and proc rates can and have been stealth nerfed in the past so any recommendations for the post of current will be based on Blight league rates but for the most part should hold true going forward.
Most of my recommendations will be based on running maps for profit, running maps for purely exp is also something people do prioritizing speed as much as possible but in my opinion if you want to level as fast as possible run pure Chayula breach stones or 5 way emblems as the difference in exp penalty from being in an 84 zone vs an 83 is substantial.
Map choice can be dependent on general strategy, are you going to position a Shaper's stronghold on your map and hence not kill the boss, or are you going to bounce your influence between shaper and elder and kill the boss each time. My personal recommendation as of 3.8 Blight league with the master mission changes would be to kill the map boss as killing the boss of each map provides a 40% chance to give you a master mission. The main things to consider when selecting a map is
1.) Map Layout / Monster Density / Monster Count
Museum is a shit show and there are a lot of maps like it, they require back tracking can lead you in the wrong direction or just have poor monster count / density, impacting the effectiveness of modifiers like beyond, and with poor monster count increasing your costs per kill and lowering your speed and return rate. Some 'poor' maps do have good div card drops though and the less people running them in the league the better those cards will be for profit and certain layouts can be better for certain builds ie. open maps for bow skills that chain, 1 way 'tunnel' maps for skills like cyclone.
The main thing I'm talking about here are map specific div cards and items that only drop in certain segments of the atlas. As far as determining what map drops what div cards it stays the same between leagues so you can use the wikis reliably to know which maps drop which cards, the value of div cards will change between leagues and this can be dependent on a number of things for example legion league saw an all time high in value for doctor and nurse cards due to the effectiveness of headhunters in 5 way emblem runs and also the lack of nemesis as a Zana mod making it impossible to chance or ancient orb a headhunter within the league. Items that drop from specific segments of the atlas change between leagues and as the atlas is mixed up. Information on wikis for this is generally unreliable and inaccurate as to what maps drop what items. There are images of the atlas that get released every league detailing what segments drop which map specific items, go off these images when taking into account these item drops. In blight league bone helmets were one of the best items with ilvl 86 normal bone helmets starting around 2 ex a piece and elder i86 bone helmets holding 6 ex well into the league. Typically i would recommend basing your decision here more heavily on the div cards the maps can yield but once again is meta and league specific, I would also not recommend farming doctor cards with the recent drop rate nerf is 3.7 and choose cards that are more reliable.
The number of bosses a map has is also an important part in map choice. More bosses = better as for sextant mods like bosses drop currency shards and fragment drops from corrupted bosses contribute a great deal to profits and when keeping your twin maps for currency shard sextant maps you can have up to 6 bosses dropping currency shards ending up with significant profit when these sextant mods appear.
1.) White Sextants Only
You should be running white sextants only if you only care about running maps fast going off the raw drops of the maps and prioritizing exp without messing around with combining specific prophecies with sextant modifiers to make those super profitable sets of maps. Use white sextants only if you want to zoom zoom and get more exp.
2.) Yellow and Red Sextants
Yellow and Red sextants are more expensive but hold much more potential profit that more than make up for the increased cost. It is my recommendation that if your map of choice lies in tiers 1-5 of the atlas that you should shape the maps around it so you can apply all yellow and red sextants to your map while running.
3.) Sextant blocking
You cannot have more than 1 of the same sextant on your atlas at the same time so when you are applying sextants you want to apply it to all the maps you plan to sextant before rolling over modifiers that are not desirable Starting with the lowest tier you plan to use then progressing to the highest typically going like this Yellow maps > Red Maps > rolling over yellow maps with bad mods > rolling over red maps with bad mods. This is a rather minor thing but will save you sextants in the long run from less frequently rolling mods you don't want.
4.) Sextant Modifiers
Anything that doesnt add monsters/ item quant or loot. or is just not many monsters
Maps have 20% quality
attack speed and move speed mods
unique bosses drop unique items
Anything that adds monsters or item quantity to your map.
Area contains addition elemental monsters that deal elemental damage
Magic Pack Size
Rare Maps contian additonal Rare Monsters ...
Area contains Breaches
Area contains abysses
Area contain hunter traitors
Mods you combine with propherices / specific zana mods for mass profit
Tormented monsters drop scarabs
strongboxes are rare and corrupted
strongbox monsters have 500% item quant
Areas contain Master
Nemesis Monsters drop 3 additional currency items
Area contains legion encounter
Prophecies are another good point where where can add monsters / item quant or even some unique effects to our maps to improve our return for a very low cost and a little bit of micro managing. Personally i have 2 tabs set aside for prophecies while mapping (Hopefully 1 day they will be stack-able), 1 tab for common use prophecies (anything that adds monsters or quant) and another for specific use prophecies (prophecies i want to use in conjunction with specific sextants or maps to maximize returns).
1.) Rolling Prophecies / Prophecy Blocking
You can buy prophecies but it is much more profitable to buy silver coins and roll them yourself rather than finding people to buy them off and trying to buy bulk a bunch of different prophecies, it just isn't worth your time. There is also the chance that you get a really expensive prophecy while rolling your own like a expensive fated unique or 6L or even 5L early league and make a killing. For reference i was buying silver coins at 3:1 chaos in blight league and easily breaking even on the prophecies i didn't want to use for mapping without hitting anything expensive.
When you go to roll prophecies you want to do it in bulk, as much as you can reasonably afford i would recommend at least 1k+ silver coins but ideally more, the reason for this being we want to block prophecies and this basically requires us to remove some of the ones we have before rolling and removing everything at the end of rolling so the bigger the lot we can do it in the less the upfront cost impacts us.
Since you cant roll 2 of the same prophecy or 2 of the same prophecy in the same chain we want to block common ones that are more or less useless and prophecies that are expensive to seal (the chain ones). Some chain ones are useful to run as they provide monsters to any map and we can only block 6 so we do the best we can do.
Prophecies you want to block:
The Lost Maps
This will leave you with 1 spot open for rolling your prophecies, there are a couple you can complete immediately instead of sealing them to delete or use for later.
A Valuable Connection (if you have sets of chaos recipe ready can give you another chaos)
Golden touch (keep a stack of orbs or transmutation and orbs or scouring in your inventory with some good ilvl jewellery, 3 mod jewellery ready to be multi-modded can sell for exalts if you are lucky and hit the right mods)
The Beautiful Guide (chisel unique maps easily or save chisels on your maps of choice, keep a stack of chisels and some maps in your inventory)
Erasmus' Gift (if you quickly run through a vaal side area will give you a 20% vaal gem at the end)
The Rest you want to be sealing for later use or deletion, I try to sort as i go into ones i plan to use for mapping, ones i will sell and ones to vendor (easier to vendor than to delete).
2.) Proccing Prophecies
This pertains only to map modifier Prophecies. They are limited to 1 per map and don't have an 100% proc rate so you usually want to be using quite a few to try and have 1 proccing every map.
Typically i apply them every time i apply sextants so fill up to 7 and end on 4 assuming 1 procs every map. You may want to not fill up to leave room for prophecies that can proc in map to use as you go but i find these aren't worth the time and hassle to use so either sell them on in bulk for things like Kalandra's craft or vendor them.
From my testing I've found that prophecies attempt to proc on a 'last in, first out' basis. This means that your most recently applied ones will attempt to proc first then if it doesn't moves onto the next most recently applied and so on. This is important to know for 'Specific use prophecies' so that we don't have to empty our prophecies every time we want to try and proc a specific prophecy for a specific map or sextant modifier. Though i have found that a specific prophecy may proc less frequently based on having more prophecies that can proc active. I don't currently have the sample size to verify this or if it is just an observation bias, so my current method for applying specific use modifiers is if i come upon a sextant i want to use 'Specific use prophecies' on i wont fill back up to 7 but rather just add the 'Specific Use Prophecies'.
3.) Common Use Prophecies
These are anything that add Monsters or Item Quant to the map, I will list them roughly in order of what i find best to worst but this list wont be exhaustive or 100% accurate to what is actually best.
Tempests (not Vaal Winds) - better with higher monster count maps
Soil, Worms and Blood
The Cursed Choir
The Hungering Swarm
The Trembling Earth
The Brothers of Necromancy
The Four Feral Exiles
The Fortune Teller's Collection
4.) Specific Use Prophecies
The following are more common use prophecies but have some stronger synergies with specific sextant mods and maps so would keep 2-3 aside for use in those specific scenarios
Bountiful Traps - 500% monster quant strongbox sextant and rare corrupted strongbox sextant
Plague of Frogs - beyond sextants / maps
Plague of Rats - beyond sextants / maps
The Twins - Nemesis monsters drop 3 additional currency items sextant
The Undead Brutes - Nemesis monsters drop 3 additional currency items sextant
The Deadly Twins - Harbringer Sextant if you don't have a good supply of twinned maps
The following prophecies should only be used with their specific maps and remember to remove them if they don't proc and you have finished the group of maps you wanted them to proc on.
Possessed Foe - Possessed monsters drop polished and gilded scarabs (rusted scarabs isnt usually worthwhile at price you can sell prophecy at)
Monstrous Treasure - 500% monster quant strongbox sextant
Vaal Winds - High Monster Count Maps
Rolling and Sorting Maps
I will go over my general strategy for rolling and sorting maps assuming your character can run every map mod, you may want to roll over certain mods if your character can't or has difficulty running them.
This is all dependent on the cost of whether corrupted maps require Vaal orbs to use Zana mods on (as of 3.8 blight league they don't).
Identify and scour to white if applicable.
Chisel to 20%
Alch to rare
Chaos spam till at least 80% quant.
If I'm very low (<3) on beyond or twinned boss maps I don't vaal them.
Don't Vaal any maps with both Rare Monsters have Nemesis mod and beyond on it.
If < 100% Quant Vaal.
When you corrupt maps and they go unidentified the mods on them DO NOT CHANGE so before vaaling make sure you know what maps have what on them so you can sort them appropriately.
I Sort my maps as follows
High Quant Twinned maps - Run with Harbringer Sextant
Nemesis + Beyond maps - Run with Nemesis Sextant
High Quant Beyond maps - Run with Beyond Sextant
Phys / Ele Reflect Maps - Run with Players cannot take Reflected Damage Sextant
Corrupted Un ID'd Maps with no special mods - Run with increased IIQ from Un ID'd maps sextant
8 Mod maps
Lower Quant Maps
What are Available as Zana mods changes from league to league, they aren't all always available but i will go over all the current known zana mods that don't affect what map you are running or map tier.
The number of additional encounters and cost of each mod changes between leagues so will leave as general as possible and you will have to evaulate which mods are best for general use within each league based on the economy and costs of each mod
Warbands - Use with Possessed Monsters drop polished / gilded scarabs sextant and Possessed Foe Prophecy
Ambush - Use with 500% IIQ from strongbox monsters sextant and Monsterous Treasure and Bountiful Traps Prophecy or Strongboxes and Rare and Corrupted Sextant with Bountiful Traps Prophecy
Nemesis - Use When trying to chance a Headhunter
Harbinger - Use with Harbringers Sextant, and general use depending on costs and whats available
Beyond - Use with Nemesis and Beyond Sextant, and general use depending on costs and whats available
Here i will go over combinations of sextants / maps / prophercies / zana mods / scarabs / fragments i use typically in conjunction with one another to maximise my returns.
Typically these are prompted by rolling a specific sextant.
Possessed monsters drop Polished / Glided Scarabs Sextant - Any Map - Possessed Foe Prophecy - Warbands Zana Mod - Torment Scarabs on Gilded Sextant (Build Dependant)
Beyond Sextant - High Quant Beyond Map - Plague Prophecy - Beyond Zana Mod - Gilded Breach, Gilded Perandus, Gilded Cartographers, Gilded Divination (Map Dependant) Scarabs
strongboxes are rare and corrupted Sextant - 8 Mod Map - Ambush Zana Mod - Bountiful Traps Prophecy - Ambush Scarabs
strongbox monsters have 500% item quant Sextant - 8 Mod Map - Ambush Zana Mod - Bountiful Traps + Monsterous Treasure Prophecies - Ambush Scarabs Gilded Cartographers, Gilded Divination (Map Dependant) Scarabs
Nemesis Monsters drop 3 additional currency items Sextant - Nemesis / Beyond Map - Beyond Zana Mod - The Undead Brutes + The Twins Prophecies - Gilded Breach, Gilded Perandus, Bestiary Scarab, Ambush Scarabs
Harbringers Sextant - Twinned Map - Harbringer Zana Mod - Tempest Prophecies - Harbringer Scarab
Area contains legion encounter Sextant - 8 Mod Map - General Use Zana Mod - Tempest Prophecies - Polished or Gilded Legion Scarab
Fill out the rest of your map slots with Gilded Breach, Gilded Perandus, Dusk Fragments, Dawn Fragments in that order for High Quant maps and Rusted Breach, Rusted Perandus, Dusk Fragments, Dawn Fragments for Low Quant maps.
I'm sure there are things ive missed and things I don't know so feel free to add any aditional advice or information you have and i will do my best to communicate with you if you have anything to add or any questions.