The size of the lift won't cause you MPG to drop, the size of the tires will.
If money is a concern do a 2 inch budget boost and if still want more lift add a 1" body lift. If you want it to do better off-road get some sway bar disconnects.
I have known a few people running this type of setup with 33's and thing worked just fine.
If in the future you decide you need/want to go bigger or better you won't have much money invested. The 1" body lift is a good mod for any Wrangler, built big or small.
01 TJ, 34 Super Swaper 34x10.5 bias, Winch, locked, belly up, some armor.