Brand new to anything but tent camping

Although addressed in other posts, my prefernce is a moderate 230ah battery bank of (2) 6v deep cycle golf cart batteries. I don't boondock, but want the option if necessary. Assuming your rig is 30a, get the 15a and 50 adapters, an extra 25' 30a cord, water hose made for drinking water, a tank filling nozzle if required for filling the tank, and a regulator if hooking up to the city water connection.
Also park power is notoriously poor, so consider a surge guard that also disconnects under low or high voltage. While pricey, an power boosting transformer can also allow you to use low voltage park power, which has saved us on several occasions.