Soldier, i thought medic but then people would depend on me....
and i want to be on the front-lines fighting and giving ammo.

I I think I will probably play medium medic first, medium so I can decide whether I'd rather be faster or stronger, medic so I can watch the other classes in action to get a feel for it, heal myself when I make rookie errors, and get lots of xp early on, however, for most of the game I'll probably go soldier and operative, as I'm not very keen on being a sidekick medic, or being as macrostrategic as an engineer.
That said I do like the idea of fighting to get to MG points and ticking bombs as an engie, and being able to hit, run, recover and hit again as a medic.

First medic, then probably engineer.

I'll probably try the soldier first because it's the one that (I think) is most simular to other games, so I learn the controlls easily and then i'll try the other classes.