>>32577858I don't think they're the best games, but I think either X/Y (Referred to as XY) or Black/White (Referred to as BW) would be some good ones to start out with.
XY has quite a lot of Pokemon in it with and a fair diversity in terms of types if I recall correctly, so you might be able to get a grasp on type match-ups a bit easier. They're pretty easy as well with the Exp All existing, so you shouldn't have to grind or anything.
I haven't used Citra (the 3DS emulator) before so I don't know whether it's a pain in the ass or not, but if it's easy like the other handheld Nintendo emulators, go with XY. If Citra is a pain in the ass I'd recommend BW since they don't rely on the previous games too much, have a decent variety in Pokemon and their types, and they're not too outdated, but still easy to emulate.
By the way, Citra is apparently a decent 3DS emulator, VBA is good for any GameBoy games, and DeSmuMe is decent for DS games. There are other emulators for GB and DS games, but I haven't tried them so I can't say whether they're better or not.