Re: good tire size?
I'd go with a 235/75r15. The stock rims are fine with it. It has much less mass than the 30" ...and has within .2"=/- of the same height (both are really 28.xx in height)...is widely available at about 60% the cost of the 30". Cash and carry Generals are anywhere from $36-60 depending on how "LT" they are. I doubt that you'll see a BFG in a 30" for under $100 mounted and balanced (some scam that BFG has with the retailers).
I believe that the stock wheels are 15x7 (they actually measure 16x8).
I'd recommend getting a set of cheap 15x7 alloys (jeep oem) used on ebay. They are readily available at very reasonable $$$ since everyone wants 15x8. The weight reduction should offset the added tire mass/height. With the 4 banger I would think that tall and skinny would be the way to go.
BTW- YOU CAN FIT 33" tires under the stock TJ WITHOUT ANY LIFT!!!!!!!!!!!!!!!!!!!!! I did it. Now it looks like a bloated rollerskate ..but it works JUST FINE. The 33x9.50 does require a 15x8" wheel .........and the steering stops WILL have to be adjusted ONLY BECAUSE THE RADIUS OF THE TIRE IS SO MUCH larger than the 28.x" ..30" tire.
A simple spacer lift or 1" body lift makes it work just fine ....you can't flex ...but the ground clearance is the same. Again ..if you go with the 235's ....they're the only thing that you have to buy.