just check and replace everything.. Dump the stock carb first, go with an MC2100. Then dump the ignition and go with an HEI set up. change the plugs, fuel filter, and air filter.
Another thing often over looked is your brakes! If you have one that is sticking, then it will dramatically drop your MPG. Also, pump them tires up about 5lbs over what it calls for. I run my J10 at 40lbs, and get about 1-2 more MPG when I do. My big GMC runs 75 is all 6 tires. Basically, the higher you pump your tires, the easier it will roll, increasing your MPG.
Another thing is to clean out your Jeep. Get rid of any access weight you don't need. In my work truck, by the end of a month of working, I find myself with about 400lbs of extra tools. Everything from an air compressor to breaker bars, to just general scrap steel. Of course your jeep doesn't carry quite as much stuff, but every lb of extra weight will hinder your MPG, lower your power, and cause things to break easier.
There's a lot of things that you can do to get your jeep running better, and getting better milage. most of the things are super simple, and will cost next to nothing. I've read that synthetic fluids in the axles will give a bit more MPG, along with synthetic fluids in the tranny and transfer case. Mobil 1 is the best I've read about.
Stay away from any of the stupid 'guaranteed to increase MPG' crap. You don't need a tornado, a fuel magnet, of any other type of thing. If they were THAT good, the factory would use them, or something similar, to help sell cars new. Most of them are nothing but a gag.
Good luck, and keep us informed on what you find out.
1988 Wrangler 89000 miles, no rust, no rot, all nice and pretty.. Runs down the highway really nice too.. This is great fun.