As said above there are a lot of variables but I'll tell you what another amateur (myself) has done.
I have a FWC project m bare camper shell that came with some led lighting and a max fan. Since I acquired this I've added a 55l fridge, more lighting and several usb outlets. My power comes from a Battle born 100ah battery that is charged by a Redarc 25 amp bcdc charger that charges from the truck and an Overland solar 160 watt panel. The longest amount of time I have stayed in one place with out starting the truck was 6 days and in that time we ran the fridge continuously, charged stuff like headlamps, cameras, iPhones and tablets. Our battery always stayed above 13v. We have a fairly minimalist camper setup but I think a robust electrical system for what we need. I'll probably add more stuff as time goes by such as a diesel heater that is next on the list but I'm pretty sure our system will handle it fine and if we are moving every day as in driving the truck, I probably wouldn't even need the solar panel but its nice for those extended stops.