Off the top of my head:

You are going to need levelers… boards are fine but you will need something.

I’m a big fan of the zero g hose: https://smile.amazon.com/4001-50-Lightweight-Flexible-Durable-Kink-Free/dp/B014M9PEXC/

I have never found a need to use RV toilet paper.

An RV patio rug is nice to have for some campsites.

Edit

A brass hose 90 (strain relief) and Y with shut-off (so you can hook of a garden hose for washing things or your black flush)

https://www.amazon.com/dp/B07S85ZZ4P/

https://www.amazon.com/Garden-Hose-Splitter-Way-Splitter%EF%BC%8CHose/dp/B08S2T7WC9/

none of the links I shared are price checked - just reference.