I feel ya. If I ran a GBB I'd start out with 4 probably. It helps that I have somewhere between 20-30 AEG mags haha. I pick them up when I find good deals. I've got E-Mags, P- MAGS, hex mags, MAG metal mags, and Elite Force mags. And that's just my M4 style mags haha. Don't even get me going on my SR25, AK, SCAR-H, M40A3, and pistol mags haha.
***EDIT*** I just realized I have a problem haha.