eh, it's 25 bucks, ain't like it's a whole hell of alotta money : / unless you're poor...which most people aren't, I buy one every few months, just to get a character and get 50,000 GP off of it, but thats about it...
EDIT* Also, I like the M416 CQBR, you can't get that with GP, or atleast not an exact match until you are high ranked. and the P90TR is nice as well, but ya the gold-plated, steel, etc. guns are a waste, they just make your gun look cool, so if you do get a gun, get one thats actually gonna help you out in-game. I just say get a Character for 30 days, activate it, and you get 50,000 GP off of it, then just spend the rest of the NX on custom Crosshair, etc.