I am running wire underground to a guest cabin in PVC conduit that is 150ft from the main 100amp panel. I will be using a 30amp double breaker in main panel. The sub-panel is 70amp(because it was free), but will have two 15amp breakers. One breaker will be for 7 outlets, the other for ceiling fan/light, and approx. 5 can lights(75 watt each). I will have a small cabin fridge and lamps basically plugged in to the outlets. No A/C or large electrical equipment. Coffee pot and micro possibly as well.
My question is: What is the minimum gauge 3 wire plus ground that I could get away with? Could I get away with 10/3???? This is a remote cabin and inspection/code isn't an issue. Obviously, I'd like to be safe and will have two ground rods coming from the sub-panel's ground bar.