Chocks for your tires.
Something to use for leveling under your tires (your choice, lumber to Lego blocks and how much is up to you) and for your stabilizer jacks.)
Water hose. (which you are getting)
Sewer hose. (which you are getting)
Electric extension cord for your camper. (here again, every campsite is different regarding the length you need, and it's possible the one in your camper is adequate for the moment).
After this, absolutely everything else is for your own comfort and enjoyment and your lifestyle.
Here's a few links to some "lists" of thing to consider. Again, all this depends upon your personal life style and your comfort level. You don't need to go out and purchase "special" items to outfit your camper. Everyday items you use around your home is what you'll use in your new camper too. Nothing special there.
WWW.rv-camping.orgChangin' Gears RV check listsStocking an RV -- RV.net forum stickyThese will give you boundless ideas!
You do not need to go to any kind of specialty stores to get what you need to outfit your camper. Anything you use in your house is what you'll use in your camper. WallMart is your friend. But if you're looking for something special, Camping World, Cabela's, or any number of sporting goods stores or outlets. Don't over look yard sales, flea markets, and even your local grocery store. You never know where you'll find that perfect 'gadget' you really want for the camper!