It seems you have a Sahara.
With the standard gearing (3.21), stick with the original diameter -32.
If you go bigger, your Jeep will not be able to get out of its own way.
Only go bigger if you have optional gearing (3.73 or something like that).
As for the width, I would stick to something really close to the originals. I don't like the idea of spacers or non standard offset wheels due to the added strain they will put on wheel bearings. The offset of the wheel is designed to place the most stress directly on the middle of the wheel bearing.
As far as clearance is concerned, turn your wheels all the way to the stops and look carefully to see how much clearance you have left between tire and anything else (frame, fender flare, etc).
And remember, bigger tires are heavier. That means a less comfortable ride, poorer handling (don't need that in a Jeep) and a guaranteed loss of ga$ milage.