Welcome to the world of enjoyment Roy.
As for basics, here are a few to start, and I am sure others will add to the list.
Hitchlock, wheelclamp, 110amp Battery, fresh water container(aquaoll or waterhog), waste water container, same makes, gas bottles, Butane is ok for summer use, if you plan winter vanning you will need Propane, and as the connectors are different, a pigtail connector for each type of gas.
Toilet chemicals, blue for the waste tank and if you like, pink for the flush water tank BUT,,,it has been found that adding the pink can cause algae growth on the flush water tank and that is not a good idea as it can cause problems with the flush.
Bedding, cutlery and crockery