If u have good items choose striker because striker has the best damage in all class of all race's..
If u dont have good items choose to be spec(for support) or trapper..
Dont worry dude. Time will make u strong here..
If you have good items try to be def type gunner/striker. Poor items be a trapper. Trappers can kill donors if you know where to put.
If you also have good items you can be a spec x melee. Good damage and hard to kill. If you got poor items you can be a support type spec.