Starting as simple as possible, you will find out as you go along, what you really need AND what you really want. Nothing wrong with coming to an understanding of what actually makes you feel comfortable.
For me, it's a comfy place to sleep, which can be either a bed or a hammock. And sufficient pillows of the proper kind.
Next, a plan for toileting. Again, I'm flexible, as long as I have a plan that works for the situation.
Food is always good. If I have a fridge, I use it. Otherwise, I'm OK with non-perishable eats, plus whatever fresh stuff I can keep cool for a day or two till it gets eaten.
Shade is important to me, so I have various tarps and even a Clam shelter, because shade is really important to me. And I carry a couple of chairs and a roll-up aluminum table, and a patio mat that keeps the dust down in my camp.
Then there is the question of storage for all of the above, plus tools, clothes, etc., and of course water.
As you can see, your kit will come together quite naturally, according to your needs. I bet you could walk out the door with only your keys, wallet, and any prescription stuff you may need, and within 3 days you would know exactly what-all you need to fit out your mobile living space.
The Dire Wolfess