TenOC had a good recommendation! That said, if you are truly boondocking....water will likely be your most important item.
The black tank is probably the next issue, fill time can be extended if.... the man of the house can use what “Mother Nature” provides. Wives generally don’t prefer this method! ;)
Batteries: depending upon your usage, season, and charging capabilities....you may only need to run a generator a few hours per day, or may satisfy your needs with solar panels!
Cold hard reality is, if you want to do lengthly boondocking often... you may need to reconsider your RV,s capabilities!