For a 2.5" lift you can go cheap, but generally the best cheap lifts will be lifts that don't lift much. Like the Rancho 2" progressive lift, which tends to only lift around 2.4" up front and 1.5" in back. That lift should be just enough to run 35's, but some 35's are bigger than others so it may be close. Worst case, you might need a pair of 1" bump stop extension in back if it rubs. You also might want a set of front shock extensions to compensate for the 2" bump stop extension included in that kit. Even with this lift some find they still need to add caster correction. A set of longer lower front control arms or geometry brackets will solve that.
Other 2.5" lifts tend to lift closer to 3" or more up front, and that means that are more likely to require caster correction. That is because lifting changes caster, and caster is what makes your Jeep drive properly or not. You can get a decent 2.5" lift for around a grand, there are a few brands out there. AEV, TeraFlex, MetalCloak, JKS, etc.
I like the TeraFlex based Most Popular Lift on the Wrangler Forum, as can be had from Allen
. But you can't go wrong with AEV, or any of the others.
As to body lifts, they aren't very common with JK / JKUs. They are more common on older Jeeps. JK / JKUs don't normally need them.
As to gearing, first you need to know what gears you have. But if you are going to 35's, I would want to regear. If you have 4.10 gears you might be happy with 35's. But I wouldn't be. If you have 3.73 or, worse yet, 3.21 gears I really would plan on a re-gear. But that is up to you. Everyone has their own version of what is acceptable performance. Some are fine with the loss in performance that comes from running larger tires. I am not.