A lot of times, dealers throw in a "starter kit". Usually a freshwater hose, (sometimes it's 10', sometimes it's 25'), an adapter from 30 amp to 15 amp outlet, a cheap sewer hose (that's next to worthless), maybe a water pressure "regulator" (if it's there, throw it away. It's just a brass water flow restrictor, not a real regulator). The starter kit usually has black tank treatment (that's really not needed) and maybe a couple of other small things. The biggest thing is a notepad and pencil. As you come across things that you need/want, write it down.
Try camping out in your yard, or very close to home. If you really need something that bad, run to the house and get it, or run to Walmart.
A decent sewer hose is near the top of the list, Valterra and Rhino are both popular brands. I have both, and I like the Valterra better. You obviously will need enough freshwater hose to supply your RV too. When camping, you will most likely spend more time outside than inside. Get some COMFORTABLE outdoor chairs. One of the first things I add to mine is covers over the vents on the roof so you can leave the vents open during the rain. As far as dishes, a lot of us use Corelle. It's kinda heavy, but for the most part, they don't break.
The biggest thing is, don't go crazy buying "all things RV & camping", it's easy to get caught up doing that, and a lot of it really doesn't get used.