The wisest thing you can do first, is stay at a full hookup campground close to home for about a week. That will give you time to learn the ropes. Most of your fellow campers will help if you ask. If you forgot something critical, you can go home and get it.
Take a notepad and write down what you forgot to bring on the first page. If its something critical, you can run home or to WalMart to get it. On the second page, write down what you brought but didn't use. That doesn't mean you won't use it eventually, so call it your 'maybe I don't need this' list.
Things I needed but didn't bring:
20/30 amp and 30/50 amp 'dog bones' for electric hookups.
Several things for the bathroom and kitchen. Spray cleaner, sponges, rags, bath soap, dish soap, a plastic dish pan, drain board and rack. A can opener. A coffee pot, and coffee. A cutting board. A couple of sauce pans and skillets. A box of wooden kitchen matches.
Aspirin for headaches - you'll have a few. A good first aid kit. Band Aids. Bedding, including a blanket and pillows.
Things I brought and didn't need:
Place settings for 4 in the kitchen. I travel alone and there just isn't anyplace to store dirty dishes.
And don't forget a sewer hose and white (potable) water hose.