Don't play this pay-to-win.
On a more serious note, if you really want to, just buy the Desert Eagle, M4A1, AWM, and AK-47. That's all you need. Please don't buy ZP... just don't fall into that hole.
As for actually being ingame, I suggest practicing on Egypt/Ship to improve your aim. Play SND to improve your tactics.
Regarding hacks - don't use them. It's not that fun for long.