For me, I take what I want or think I want and don't worry about it.. :)
If I find I want something and don't have it, I pack it next time!
I know I've got my #5000 GVWR TT weighing in at #5000 (and probably a bit over since it weighs #4500 on the axles alone.. ;) )
I carry a full 30 gallon load of fresh water when I leave home. Take at least 3 cast iron pans and 2 cast iron lids, maul, a bunch of wood planks for leveling, chairs, table, more junk I think I might need, still more junk I need and finally, other stuff that goes in the truck bed! :)
I pack for me.. Not others.. I hate it when I need something and I know I have it at home! I used to even bring along my generator when I knew I was in a hookup site!! That was because "if the power goes out in the park, I'll still be able to have power".. Well, after 12+ years of State Park camping, the power has never gone out, so I stopped taking the gen after about 3-4 trips after getting it.
I figure anything you add to your truck/trailer to go "camping" is what you are hauling, so it counts! :)
Good luck!
Mitch