Welcome. You're gonna want to read a lot.
1st - What will you do with your Jeep? That is the most important question.
2nd - On a daily driver, I would go no more than 2" of lift on 31 inch tires. Go bigger and you'll spend a lot more $$$.
3rd - Don't count out the 15" rims. If you look at pics, you'll see that big tires on small rims doesn't necessarily mean "bubble look." Staying 15" gives you more protection on the trail. It's also another way to save $$$.
Best advice - Find a local Jeep club. Go to an event. Look at a lot of Jeeps. Go with them off road with your Jeep "as is." Then decide what you need to do.