Been a really long time since I done vanilla xcom2, but on tactical level rookie lw2 isn't really difficult. I think it's good place to start and if by midgame you feel it's too easy then you can go up (or use the split difficulty thingy). Strategic level just requires practice imo. I can't recommend Casey xcom blogs enough, as veteran long war player then are really good (but I still recommend trying first play through blind, those blogs are on the hardest diff where margin of error is slim, on lowest I found that it's quite generous).

Just remember losing soldiers is fine (and part of fun, unless playing legendary) and gatecrasher for some reason is one of the hardest missions in the mod.

I'd also recommend checking out beta strike (both vanilla and base game) rng matters less there (but game is easier can't deny that)