Depends on what your boondocking is like. Do you boondock for long? Just a weekend or for weeks on end?
If just for the weekend maybe just stick with the cheap Marine battery. Fill with distilled water, never tap.
Do you have any solar?
For the campground phase of your camping experience then a small exit sign 12v battery would be enough to get you past the drive portion, you don't need hardly any battery, so then now you are just getting battery for that Fall when you boondock.
Boondocking in the fall when it gets cold means running the furnace? The furnace fan is a power hog, so after one night you will need more power than the battery has left. You need a big battery bank (two batteries) or a way to top off the one battery. Solar works perfect, but some ppl use generators for a few hours to charge back.