for batteries, it's really just a combination of the NUMBER of batteries(amp hours), the state of your batteries(condition/specific gravity reading for each cell), and 'how' you are using them...
DURACELL 6v GC2 batteries are a good value at SAMS or Batteries+Bulbs stores... sometimes on sale at $99 each or less. The more you have, the better, of course.
Solar? Maybe, maybe not. It really depends on 'where' you are 'off-grid'. In the shade, no. In the open, it might help to keep from running the generator as much, but it's not a 'magic pill' to be 'solar only'... that's no reasonable for most of us. It's also not cheap.
two Campers, two Electric cars
former diesel pusher traveler