buy guns for weeks if you can, you'll save gp. Also dont waste money on uniforms and stuff that doesnt really help you all that much, like extended clips or fast reload clips. I rank up pretty fast usually every 2 or 3 weeks and I'm a CSM2, so mostly you just have to save gp where ever you can, and if you get nx get the xp increase pass, its worth it completely. If i had nx I would have it, then I could rank up much faster, which would be nice.