Get the Saiga, and anyone within 10m is a dead man. Its a general use gun, so you can equip it with any class. Its great for when you are doing support stuff like Engineer or Medic. Just dont bother trying to take anyone down med+ range. Once I started using it I leveled up quick. The Saiga, XM8 and M24 are the only guns I trust so far, but I'm only level 11. There are a couple of guns I have been killed by that I know are good, but I have to grind away to get them.
I wish there was a general use assault rifle. I would rather use that for recon and medic. Also, if you see someone take a flag, just run over there. If you get there in the last sec you get 50 points. If you are spawning and see a squad mate near an objective, obviously spawn there. If a squad mate is in a tank, spawn there, and go along for ride. You get a piece of the action for anyone killed by the tank. If you dont go after objectives or use a class that helps others, leveling up can take forever. I have been sniping and went like 15 and 1, but got very little points. As medic, 2000 is easily achievable.