I would wire up for a minimum of full 30 amps at no less than 115 VAC capability and 8 gauge just gets you in there while 6 would be better. You might not think you'll want or need it today but it will be nice to have if the need ever comes. Cost difference isn't as much as you might think to go with the heavier wire to gain the amps.
I have 30 amps wired to the driveway and it makes a great plug in for other stuff when I'm work outside. Lawn tools, power tools, drop lights what ever I need. My closest outlet other than coach power is 50 feet of so away.