When its your first time playing use gunners it owns at low levels then why you hit 20+ it becomes a little hard using him but very good at short range battles.
Soldiers are good my favorite class they are not that good at a low level and your not experienced but at high levels it is the best Blast strike gunners and commandos and set them on fire.
Commandos are very hard to master but when used right it can pwn commandos are very tricky it comes down to timing and being sneaky. Sniper rifle and knife does ALOT of damage. At low levels do not knife your stealth isnt really that good so try to snipe untill level 5 stealth then thats when you can knife
DDD