When I first started tramping I had the basics for months, sleeping bag, small camping cooker and a peak stove, 10ltr jerrycan of water, enough tinned food / ready meals to last me the week, pot noodles, pan, kettle and eating irons, cup, and an ever growing pile of A to Z’s, all stacked in the passenger footwell and my clean kit in a hold-all on top.
There’s no definitive list of what to take and what not, each driver will have his / her own kit list.
You’ll start to ditch gear you have no use for and collecting useful stuff as you go along, try not to clutter up your cab, nothing worse than looking for gear you know you have but can’t find it for gear you don’t use.
One of the best home comforts I found was taking a bowl and sponge, if you end up miles from anywhere you can always warm a bit of water and get a quick wash, not the same as grabbing a shower but you don’t have to get in your scratcher minging.