Not an expert but I am on my third Wrangler............................
As the others say, skip the 4cyl. No advantage at ALL in MPG or otherwise & you can't tow shit with it.
Make SURE you have a mechanic go over the vehicle before you buy it!!!! Manual tranny's tend to wear out their synchronizers quickly, IMO. I got an auto in my last two Wranglers & will never do otherwise with a vehicle I buy. Too much rush hour traffic for a stick, IMO.
Be sure to put it up on a lift & look ALL underneath. Make sure the drive train has been properly serviced, i.e. fluids changed! Avoid one with oversized tires! Chances are the owner thought it was a Baja 500 vehicle & drove it like that.
Try to find one with a hard top if you can. Soft tops offer NO security for guns or stereos! You can easily take the doors off a hardtop & get all the air you want.
Be sure to lift up the interior carpet & check for mud or rust. Both would be a deal killer, IMO.
I would only look at the TJ Wranglers in the 1997-2006 years. Before that was the YJ with the GD square headlights & they had some manual tranny issues as well. CJ's are okay but are usually high mileage. The JK is too new to have a good price on it most likely.
Keep in mind that almost anything on a Wrangler can be changed out by the owner: axles, tops, seats, carpet, wheels, etc. etc. so if you find one in good mechanical shape but you hate something about its looks, you can easily change it.
Best parts options are Quadratec & 4WD Parts. Both carry many of the same things from the same mfgrs but they also each have proprietary items as well.
Good luck!