I was looking for a link to a 50 minute youtube video I watched about a year ago but couldn't find it. It showed all of the little things that make living in a small space safe and comfortable. That's where I learned to use a couple pieces of 2X10 and 1X10 for leveling, Y mount for your hoses at your site, 90 elbow for fresh water supply, pressure regulator.
Things I haven't seen mentioned: axe or hatchet and small sturdy shovel, gas lighter with long nose, to light stove. insect repellent. Some minor electrical tools and parts. check continuity, replace fuses, repair crimped wire connections.
I personally have 2 5/8 50ft hoses plus a 25ft city water hose and a 25ft black water hose. I made 5 12x12x6 blocks of wood and painted them, for leveling. 30 ft. 10ga extension cord. Battery cables, nice work gloves for setting up/down and rubber gloves for blackwater work, big can of Lysol spray (spray everything before and after), several small bottles of hand sanitizer to use as needed