get an electric, most bang for buck, and you don't have to buy gas, if you want an emergancy back up get a gas pistol (I went on a gas pistol craze, I have a WA beretta 92fs w/full badging, and a pair of some of the only Glock 18cs with full badging to make it in the states from KSC)
I have a p90 with a Ti barrel extended into the sliencer, full rail system, a nade launcher somewhere, it's got all the hopped up goodies (all the "silent" stuff), a MP5k with silencer extended Ti barrel and a pdw stock, it's got the new spring, motor, gearing, piston, all that good stuff. Both the AEG's need work. (my PSG-1 will never run again)
I'd suggest take it easy at first, I got all out into airsoft right away because my best friend was and I got a good discount and free gun work, which doesn't help if you get as much crap as I did and played as much as we did. It can be as expensive as you want it to be though. I'll sell my mp5 to ya, gotta figure a fair price, and get a few things fixed on it (nothing major)