Which weapon should I buy next?

Deagle or anaconda.

Do you like to snipe? buy a sniper.
Do you have a pistol? you can buy one, sometime is useful
Do you want to stay with rifle? buy a m4, k2, ak

You have realy good wepons. But i think buy now pistol, deagle or anaconda. Yesterday i buy p228 i i have really good fun with him.

If you want an MG go fot the RPK if you want Shotgun go for the XM1014 If you Want a Rifle get the XM8 Or TAR21.

If you like sniping then um AWM or Dragunov
If you want another assault rifle then xm8 or famas
Or if you would like to try an smg then get MP5 because its easy to handle and get kills with.