You will need a min. of 15 ft. sewer hose kit which will have most of the fittings to do a dump. I would get the HD kit and also a 10 ft. extension hose as some of the older campgrounds have the dump inlet a bit far out. Also, a water hose or two. A water press. regulator and a filter. You can get most of these at a big box store or home improvement store at a better price than a camping store.
I see that you have some great advice and info from others on the forum and hope all goes smoothly on your sale and first outing.
Happy trails.