This is basically the strategy laid out in
this guide, but that thread is so wordy that I found it hard to follow, even though it's all correct.
Here's what I'm doing:
- 1. Do white maps aimlessly to get a few completions for the bonus and a decent white map pool. During this stage you don't care about which ones you're completing; having white map completions won't cause you problems later, because we're going to be using watchstones to prevent bad maps from cluttering up the drop pool.
- 2. Once you have enough white maps that you have several from the same corner region, grab those maps and do them one after another. This should spawn your first Conqueror. Run it and get your first Watchstone. Socket this Watchstone in one of the interior regions. It doesn't really matter which one, as long as you have a couple of map completions for that region so the maps there can drop.
- 3. Do the same for each of the other three corners, fighting the second through fourth Conquerors. Bank their Watchstones, don't socket them in a region. During this time, you should be getting a few drops of maps in the region where you have one Watchstone. You'll use these next.
- 4. Socket two of your banked Watchstones in a different interior region.
- 5. Run maps from the region that has one Watchstone, to spawn your fifth through eighth Conquerors (you should already have these maps because they were dropping during steps 2-3). During this time, you should be getting map drops for the region where you have two Watchstones socketed, but not anywhere else (because nowhere else has enough Watchstones socketed to drop maps of that tier).
- 6. Now that you're done with the first interior region, unsocket its Watchstone, so that it no longer competes on the drop table. Socket three of your banked Watchstones into the third interior region (one where you haven't done any Conquerors yet).
- 7. Run maps from the region that has two Watchstones, to spawn your ninth through twelfth Conquerors (you should already have these maps because they were dropping during step 5). While you're doing this, you should get map drops from the region with three Watchstones socketed.
- 8. Unsocket the two Watchstones from the region you just finished, and socket four of your banked Watchstones into the last interior region where you haven't fought the Conquerors.
- 9. Run maps from the region with three Watchstones, spawning your thirteenth through sixteenth Conquerors, and getting map drops for the last interior region.
- 10. Unsocket the three Watchstones from the region you just finished, and socket four Watchstones into any corner region.
- 11. Run the maps from the final interior region, spawning your seventeenth through twentieth Conquerors, and getting map drops for the corner region you just socketed.
- 12. You now have 20 Watchstones, meeting the requirements to fight Sirus for the first time. Do the Awakener fight. After this point, Conqueror spawns are no longer guaranteed in eligible regions, so it'll take longer to spawn the remaining ones.
- 13. Unsocket the four Watchstones from the final interior region, and socket them into a second corner region.
- 14+. Run maps in a corner region. When you finish a corner region (have fought all four Conquerors there), unsocket its Watchstones and move them to a different corner region which you haven't finished yet. Repeat until you've done all four corners. Then socket all your Watchstones everywhere (for max Awakener level), or in regions where you like the maps (less Awakener level but don't have to run maps you don't like), and farm at will.
...aaaaand now I'm almost as wordy as the guide I started from.
The point of this whole rigmarole is that
at any time after your first four Conqueror fights, the only valid drop options for maps at or slightly higher than the tier you're running are the region you're currently running, or the region you'll be running next, since everywhere else on the Atlas is nothing but white maps because you don't have any Watchstones socketed there. This makes it way more likely that you'll get the map drops you need (or you're about to need) as you go along, instead of having to buy maps to do progression.