I have always maintained that when buying a new Moho you should spend the first night on the driveway at home living in it and using all the appliances to ensure everything works (heating, hot water, shower, TV, cooker, microwave etc etc. Far better to do this at home than at a campsite and even when buying new (as we always do), you can't beat familiarising yourself when there is no pressure.
For you first time "away" I suggest you do the same, have an evening & night in the camper without leaving home and if you find you have missed something, you can pop inside for it!😁
Our Moho is permanently fully equipped and we never have to put anything into it when we go away other than fresh food.
You learn what you want/need the more you use it but as long as you have the essentials to be comfortable you can't go far wrong.
The list of things we carry is endless but as old hands we know what we need.
Crockery, cutlery, mugs, glasses, corkscrew, chopping knives, can opener, washing up kit, tea, coffee, sugar, salt, pepper, sauce, mustard, squash, sealing clips, scissors, laundry bag, binbags, matches, portable radio, batteries, torches, cleaning materials, paper towel, charging leads, first aid kit (Inc painkillers, antacid etc), reading material, DVD's, bedding, pillows, throws, clothing, spare shoes, Crocs or flipflops, wash kit, charging adaptor, robes, spare reading glasses, loo roll, towels, waterproof coats, rucksack (for trips out), umbrella, folding chairs, table, waterproof rug etc etc.
Then of course there are the items for the vehicle. Handbooks for the various onboard systems, levelling ramps (if no auto levelling), spirit level (the small 2-way camping one), EHU lead, coax lead, water container or hose (for topping up), gas bottles (Inc spare & gas spanner), water sterilising tablets, basic tool kit containing sufficient tools and bits & pieces to make running repairs (hammer, screwdrivers, pliers, cutters, adjustable spanner, gaffatape, cable ties, PVC tape, fuses etc), pegs & tiedowns if using an awning or sunshade, peg remover, etc etc.
Are you taking pets? We take Ddogs and have to take leads, harnesses, beds, screwdown anchors, blankets, bowls, toys, food, treats, medication, water bottles, towels (wet dogs are great fun in a Moho!) and their buggy.
Bicycles? If so don't forget helmets, cycle clips, locks, pump (and repair kit).
Honestly the list is endless (and in a few minutes I will probably have remembered another load of things) but you will learn as you go. If for instance you eat out all the time you will carry a lot less than people (like us) who never do.👍