Most people camp with a single 12v Marine deep cycle batteries. If you are on shore power most the time those work fine. They will even get you through a night or two not hooked to shore power depending on the load (generally whether or not you need the furnace). I camped in the smokies for a week on a 12V deep cycle battery without shore power, no furnace, no fans, generally little to no lights on. Water pump, refrig, and water heater were basically the only draw on the batteries. (lighting provided by flashlights, battery operated lantern type lights, and coleman lantern outside).
So the big questions before you go out and spend several hundred dollars, what are your "Real" needs?