I honestly don't understand it when I see people spending real money on re-skins, because the only difference between the G36E Valkyrie, the SCAR Trispear and the Double Barrel Punisher are different looks. Just a waste of cash in my opinion.
I would buy one of the female characters because they seem to be faster and you get 50, 000GP if you buy one for 30 days. Also I'd buy a P90TR or the M416 CQB.
It all depends on how you play though