The starter kits usually have enough chemicals for a weekend or two and only one roll of toilet paper. If you buy toilet paper at your local store make sure it's 1-ply and septic safe. The sewer hose is a cheap one, so I suggest a Rhino brand. Get some disposable gloves to wear when handling the sewer hose.
I don't know where you'll be camping, but you might want to pick up a 50 to 30 amp adapter just in case.
Wal Mart carries a decent supply of camping supplies at a reasonable price. If you can't find what you need there you can probably get it at your dealers.
I have bought several items online, RV Wholsalers. Here's a link.
The Original RV Wholesalers - RV Sales, RV Parts, RV Dealer, Camper Sales, Rockwood Camper, Travel Trailer, Fifth Wheel, Forest River
A portable grill is nice to have. We use paper plates and things like that alot. Of course you'll need all the other normal kitchen items plus all the bedding and bath items as well.
Other items to consider, electric tongue jack, max air vent covers, mud dauber screens for the frig, furnace and water heater and some x-wheel chocks. The kind that fit between the tires.
I forgot to mention a potable water hose (white).
The best way to find out what you need is to go camping. You'll find out pretty quick what you need and what you don't need.
Hope this helps and happy camping.