If dry camping/boondocking more than overnight, you should have a generator. A Honda 2000 or similar low-noise generator is a good choice. Plugging into your truck to recharge trailer batteries is very inefficient when dry camping, although it will help on the road.
You must use propane for appliances, but they still need 12vdc for their control circuits. Leveling up and opening slides will leave your batteries low, then two days of water pump, lights, etc. will likely pull batteries down enough more to prevent closing the slides and pulling up jacks. One gallon of fuel is all your generator will use over a weekend to keep the batteries full and permit some 120vac use for the tv, toaster, etc.
How much water you use depends on the number of people and how frugal you can be. Two of us can go two weeks when necessary on a full fresh water tank (100 gal). We carry a 50gal bladder tank for hauling fresh water and a large "blueboy" for hauling waste water.
Boondocking can be fun if you are prepared for it, and a nightmare if not.