.. ok. Here's what I'd do on a budget
Water/Fuel - goes without saying. Take plenty of spare, especially water.
Then considering a minimal repair kit, depending on how far away you will be from the nearest town (ie: drive to a workshop) and roads with daily traffic. Also consider what
you are capable and willing to fix on the side of the road / in the dirt.
- Belts - just take a spare Alt/PS. You don't need AC if that belt goes.
- Rad hoses -- consider repair tape instead of spares. Maybe take top/bottom hose.
- Filters - why? What's going to happen? You could clog your air filter -- brush/knock the dust out. Fuel filter you might clog if you get crappy fuel, but again, it can be cleaned out to be serviceable - take a bottle of meths to chuck in the tank if its contaminated. If you get a holed air filter (which you probably wouldn't notice) - you could plug the hole or put a t-shirt over the lot.
- Sensors -- I can think of six or seven that might fail. How are you going to even diagnose the problem? The most common failures (MAF, O2, knock) are not likely to completely strand you.
- Tyre diameters -- it matters less if you're on dirt where there's easy wheel slippage. Still a risk. Consider a tyre repair kit to plug up small punctures. You need a compressor.
- Some goop to plug rad (and exhaust) holes would be good.
- Busted CV boots can be bodgied with plastic bags and tape for a short time.
- Communications -- again, depends on where/size of party/etc.
- Basic useful stuff like cable ties, hose clamps, wire, tapes, decent shovel, jack plus soft-ground plate, WD-40 or similar.
- Tools to do reasonable repairs - 10mm, 12mm, spark plug socket, socket set, screwdrivers, pliers, hammer, etc.
- Consider 5l of spare oil in case the worse happens and you dump all your oil.
- maybe a couple of old spare spark plugs
And don't forget to listen to your car constantly, and just to spend 10min every day looking over your car (under, engine bay, etc) before you set off (or when you have a beer at the end of the day). Observation is 9/10 of fixing problems, and they're all easier to fix early.