I'd recommend watching some general game networking architecture videos.

Any tutorials with a tool that lets you simulate latency and packet loss will help you a lot.

Starting off with turn based games is going to help you a ton.

After you've got a handle on that it's worth looking into videos that are more specific to what you need, like fps, rts, etc... and the techniques that each kind of game uses. You'll also get an idea of how online cheating works because you'll be able to see what information each machine can read and set.