I wouldn't completely discount 2fort though. Sure, if you want to competitive, it's not the best idea, but it's a good tutorial for the TF2. The instant respawn makes it easier to practice your airshotting/rocketflecting/other fun stuff.
As for what class to choose, I would reccomend Medic because he's relatively beginner friendly and even if you suck, people will still be happy because there's a medic on the team.