First slug of RV supplies for a first timer. What do I need?

Surprised it wasn't already said unless I completely missed it.
Search the forum, beginners & general subjects. There's more "beginner lists" than you'll be able to read in a week.

Having said that, and you already having your starter list, my #1 recommendation is some method of making notes so the next time out you don't forget whateveritis. A bit embarrassing to forget that whateveritis the 2d time around. Causes problems with the better half when you forget the 3d time and it's hers...

Enjoy!