With many years of camping/exploring in the oz bush for 2 - 3 week stretches being the norm there's a lot of areas that you fine tune over the decades...
The vehicle is of course of primary concern since it has to get you there AND back. So, maintenance is important as is the appropriate recovery gear and repair gear that makes sense for where you are going (and the knowledge/experience to use it). Being self sufficient when a puncture occurs or you have to do a minor repair is obvious. So, you do end up taking a fair bit of stuff that may not (hopefully) ever be used while you're out there. It's stuff you should own anyway, so not an extra expense. Being big enough to look at an obstacle and decide to bypass, or turn back is a major plus when you are out in the sticks, better than breaking something a few hundred miles from the nearest town.
A reasonable tent, footprint, pegs, sleeping pad and sleeping bag are very important to get you rested and comfortable. You don't want to spend an hour assembling it all up and you don't want to get rained out or too cold or too hot.
The one luxury item is a decent sized 12V fridge. Having the option of non-canned food is wonderful and NOTHING beats a cold one or two when temperatures climb and you have made camp and are ready to relax. Even cold water is amazing when the temperatures are climbing up past the 90's. Since you can pack a fridge pretty full of stuff (even if all of it doesn't need refrigeration) you don't lose much storage area in the vehicle. Last year we were out for 2 weeks and no option to restock, so storage room for food becomes important as does how you store things (potatoes, onions etc) and having fridge capacity for other fresh food/meat/eggs etc. Choosing which food to eat first (more perishable) and how much will be needed to cover the time you're out there PLUS extra in case of breakdown etc.
Cooking gear is somewhere that folk can go crazy, for vehicle camping weight is not a big deal, so cast iron frypan, camp oven (if you want fresh bread or a cake or stew etc) and then something to boil water for tea/coffee. I like stainless steel (nesting cook kits) for the non-cast iron stuff. I always take a few plastic deep dish/bowls, handy for breakfast/dinner/prep... one size fits all. Stainless forks/knives/spoons.
A basic table (I recycled the legs off an old folding camp table bolted to some plywood). Chairs - now that's an area where spending some money + research time is worthwhile! You spend quite a bit of time sitting around at camp so a STURDY and COMFORTABLE chair is very important - most aren't very durable and you may only get one trip out of them. Being able to repair the chairs is important while you're out there. A decent tarp and posts/pegs so you can set up for shade or rain protection, being able to attach it to the vehicle means you can create an area protected from the elements and still easy access to the vehicle/tailgate area for cooking etc.
In oz we do all out cooking over a fire, so a decent diy hot plate to toss over a small fire/coals is perfect for cooking. Cast iron is good for use on fire. NO aluminium cookware - it'll just melt if you leave it on the fire and forget to check it

I do take a small multifuel one burner hiking stove - in case of rain or the need for a quick meal or hot water etc.
First aid kit with FRESH meds etc is something a lot of us ignore. Much of the contents depends on specific needs + the obvious cuts/scrapes/punctures...
Comfortable clothes (layers) and footwear to deal with all the weather variations that are (and sometimes are not) likely to occur. A decent bag to store it all into. Since I'm often out long enough in warmer weather, I have some clothes pegs so I can do basic de-stinking clothes washing. No need for a ton of clothing if you can layer it up if needed. A decent wind/rain proof jacket/coat so you can set up camp if the weather decides to try and give you a free shower.
I have a checklist of stuff I pack/take on trips that has evolved over many many years. These days it's rare to find something to add to the list and often I'm looking to prune something off it instead
I do have a mate that tends to have the top notch gear (at least in price) in his 4wd so where I have a 'new' table that cost me nothing he has a $200+ wizbang aluminium folding table (though with plastic clips that can break...) and various other 'gourmet' camping equipment. At the end of the day he can set up camp quite a bit faster (since he also sleeps in the back of his troopy) but we both get to the same spots, get nice and compfy and have a cold beer or two before cooking up meals.
Of course in my mate's case I think that searching out the latest $$$ item is part of his camping fun... My fun is having an equivalent item that cost me $ or nothing
As always, 1/2 the fun is getting there and that includes accruing and refining all the gear you take with you over the years.
Enough ramblings by me for now...
cheers,
george.