I've played like 60 games and barely have any idea wtf is going on, good luck lmao

My advice is to pick something relatively low impact like janitor or bartender if it's available and just try and hang out and see what happens. Or just be an assistant but people tend to ignore you or grief you if you're assistant. Some of the more complex roles, if you're interested in trying them, such as engineering or botany, are greatly benefited by figuring out how to host a private server to log on to and practice outside of a real game. Medical, at least as of a couple years ago when I last played, is pretty formulaic and as long as you know what operation you need to perform and have the supplies to do it, you can just follow a wiki page recipe.

Don't trust sec, don't trust the clown, if anyone outside of your departnent is being exceptionally nice to you they're probably going to stuff your corpse in a locker 20 minutes from now if you don't help them kidnap HoP. Learn to be robust. Rules (both social, and actual game rules and code) will differ, sometimes greatly, depending what server you're currently on, but reading the Goonstation wiki should give you approximate knowledge of most things.

If you roll antagonist, God be with you, and know that we've all royally bungled many an antag objective, most especially when new. Just try to have as much fun as you can, the points don't matter anyway.