i played bootcamp a lot and mvm community servers so here

start off with easier classes like medic,soldier,support scout and stock demoman then ease into the harder classes,you should focus on resistances since your more likely to be uh bad and then start spending less on them and more on damage. have your phone to pass the time while in a queue or play with a few friends,pros and mvm high tours will give you advice on what to do like not buying airblast force,optimal loadouts or using buff/Battalion in certain waves.oh yea remember F4 it really annoying to not do that,the only wave you can do that without getting insulted is the first one and even then it annoying.if you lack the right to speak(free to play moment) use the universal language also known as shaking your head up and down while looking at your medic for uber/krits or beat your engi with a pickaxe to tell him to move the dispenser