I don't know how big your rig is or if you have things like a residential refrigerator but if you have normal RV appliances and only plan on using it in weather that doesn't require AC or electric heat, a 15-20 amp circuit is adequate for storage, running the fridge and the odd day you might want to use it.
Lots of us dry camp with single 2000W generators that only put out 13.5 amps. Just put your RV appliances on propane and limit the use of high demand appliances like microwaves, toasters and kettles to one at a time. If you use an extension cord, make sure it is a good quality 12 gauge cord.
A 110V, 30 amp circuit is easy and inexpensive to install. Everything you need is available at Home Depot. 50 amps is overkill unless you plan on using it a lot or as a guest house.
As far as parking goes, for years ours was parked with one side on concrete and the other on 3/4 crush gravel with no noticeable difference. It is now parked on gravel with the tires resting on a pair of treated 2X10's that are imbedded into the gravel. Also works well.
