2" lift.. best to go with RoughCountry.
the bigger tires will decrease your gas mileage. And youll want bigger tires bc stockers with a 2" lift look a little funny.
you'll see a 2-3 mpg drop. i was getting 19mpg stock then with my daystar lift and 265/70/17 tires.. I went down to 15.5.. but I've had kayak racks on since the lift.. and just took those and my thule crossbars off, so I expect to get back up to 16.5-17. if you spend money on a tuner though.. you can basically get back up almost to your original mpg... and if you get a big mod bug, the addition of the tuner along with a CAI can get you more mpg than you may have had while stock!
go to the offroad modifications section and there is a lifted WKs thread.. tons of pictures in there of lifted jeeps from 2"to 4".