Agreed with everyone else. Don't bother with a revolver unless you really want it and don't care that you'll be effectively useless on the field. Get yourself something simple that you like at first, and go from there. Double stack mags tend to hold more gas, but that's not saying singles are useless. I have a WE 1911 that's actually great on gas. I also have two Glocks and a SIG.
Huge thing, just as a beginner; DO NOT go for a fully automatic handgun, IE a G18C. Not saying they're not awesome. Just saying that you'll full on dump a mag at someone and fuck it up. Semi guns have their problems. Autos compound the problem.
I'd head to a local shop and fondle guns. See what fits your hand and what you like. How well can you reach the controls, where do they feel comfy, do you like the sights, action, etc. Go with what you're comfortable with, and move on from there.
KJW SIG P226R -- WE 1911 Punisher -- KSC USP Tactical -- KWA USP Compact
KWA MP7A1 -- WE M4A1 -- WE KAC PDW -- WE M16A3 -- WE G39K