work on your recovery kit
First aid kit
air compressor- don't get the Wal-Mart one, you will be forever and half a day airing up, even with stock tires. Viair 400p is what I would recommend for stock. Larger tires you will want a bigger compressor so if you plan on going to 35's or so, spend the money now and get the ARB twin.
GPS- your phone won't work for some of the places you will be going. I use Back Country maps for my android tablet.
As for mod, to all that don't have them I recommend rock rails. Find a jeep mod shop and see if they have any old rubi rails in the trash or check the for sale ads, some one is always trying to sell those things. ACE has some inexpensive ones that seem to be a favorite for a lot of people.
As others have said, wheel it, join some of the local runs, talk with fellow JK owners find out what is working for your style of wheeling.