I boondock with 2 batteries.
If you can fit 2, 6 volt batteries in, get high capacity 235 AH type. That gives you a 235 AH bank at 12 volts.
I couldn't do it, so I fit 2 gp31 deep cycle batteries, from Sams Club. 105 AH each, giving me 210 AH.
I can watch Sat. TV, run the heat on 40° nights and make 4 cups of coffee in the morning.
I may run the generator for an hour in the morning and 2 to 3 hours after dinner unless its a travel day. Then the charging is from the main engine.
Don't get hooked on the 50% discharged myth. You can take them down deeper. Sure it shortens their life by 1/2 , if done regularly but its 2 batteries instead of 4 that wear out, just don't go below 11.5 volts, before recharging.