As a newbie myself I would stay away from the GBBR and go with a AEG. If you're going to game it, from a mag capacity POV the AEG is much better. You're not going to have fun if you need to re-load or run outof ammo in the first 2 minutes of game play.
This is just my opinion. I was going to get the WE SCAR GBBR and decided to just get the AEG version.