The most challenging maps for you.

...Then they say that you need to build troops first and only then build money-generating structures, otherwise you won't be able to play on impossible difficulty. But I build money-generating structures first and play on impossible difficulty without any problems. Who is right??:)

To build a treasury, you need an extra 3 days and 17,500 gold, but it will only pay for itself after 11 days. Of course, if there's a lot of free money on the map, you can afford to wait. But I haven't noticed extra money lying around on the road without protection, especially at the beginning of the game. Instead, I've noticed that sometimes guests might show up after a week, and it's not very dignified to receive them without an army. In general, build a treasury.