I don't know if you want a 20 amp for fridge, running a vacuum cleaner... 30 amps...running an a/c unit...or 50 amp. While your digging...whatever you decide...I would run a big enough conduit to handle all...I would probably opt to run wire gauge sufficient for 50 amp service...that way you can upgrade the box easily if you decide to upgrade to a 50 amp outlet or a 50/30/20 RV panel.
I went overkill on mine... 80amps from the main to the pedastel...I can actually provide full amperage to the 50 the 30 and the 20 amp simultaneously... The only way I could ever use all that s to have two rv's plugged in at one while running power tools off the 20 amp circuit.
I also ran 2" PVC underground to my septic system so I can dump on the pad using a macerator pump...it would be nice, if the run from your pad is level or downhill to your sewer...wouldn't work going up hill...without a lift station...or powerful macerator and check valve....

