It's eighty for a 100 watt solar panel, about eighty for the battery power station you'll plug into.
Twenty for a camp stove, you probably have a coffee service and thermos, but a filter method is good,
Twenty for one mattress pad, and you should measure and size the plywood or something to make a flat bed. Two twenty dollar memory foam pads works for me.
The insulation I use is reflectix, about twenty five dollars would do that ceiling and make shades for all the windows, something you want to do. Duck tape is good for putting up the insulation, resist getting on the windows, but the insulation called reflectix will sit against the window without if you cut it the right size.
A ten dollar USB air filter is important.
Sleeping bags, at least two, are around twenty dollars.
You should figure out how to remove seats yourself, borrow a wrench or get one cheap, dollar store or Walmart.
A bucket toilet with lots of bags and a can with a lid to store the full ones is okay, you can throw them away in parks where people curb their dogs and you're being a great neighbor.