If you build a city in the desert, make sure that you build Petra on that city. You won't regret it, in fact you WILL regeret it if you don't build Petra on that city. Petra is the best wonder in civ 6 imo. It makes your desert city spew productions, foods, and golds like crazy. In my last playthrough, I play as Norway, I build my second city on a desert near an oasis because I need the luxury resources around the location, three kind of them! I have no other purpose for the city beside for collecting the luxury. But I manage to build Petra before anybody else. And oh boy, that city turn out to be gold. The area are completely desert bar some one - two grassland tiles. And every one of them producing atleast two production, some even three. My second city even surpassing my capital in everything. Building district are kinda problematic after the two grassland tiles are used up because you need to sacrifice the desert tiles, But I made the military district there and use the city as my unit production. It build every unit in just one turn.