First off welcome to the forum!
Secondly, you have much to learn and the quickest way to do such is by searching any questions you have in the search bar on the home page of the forum. There are so many threads already out there that could probably answer your question better than I can. However before you decide what lift you want you need to decide what size tires you want to run. If you want to stay on 31's then a 2.5" lift would do you fine. If you want to upgrade to 33's you might want to consider a 3-3.5" lift. I wouldn't get a 4" until you have money for a new cv driveshaft and sye just in case you get vibes. Check out my build thread if you want to see some of the process of a jeep on 31's being lifted and going to 33's.