Everyone here posted some great suggestions, the only things I would add is a minor repair tool kit, a note book and adult beverages.
TOOL KIT - for minor incidentals that occur while exploring the great outdoors.
NOTEBOOK - since this is your first you can start your diary first thing upon picking it up. We started ours with camping experiences in the front 1/2 and in the back anything we "wanted" or "needed" as well as encounters we faced.
ADULT BEVERAGES - for when your sitting around that campfire at night admiring your new camper and saying "what the hell did we get ourselves into" LOL.
PS This new found lifestyle is addicting and expensive at times