How much water do YOU use a week? ( Misting system question )

I was adding up some of the expenses that comes with poison dart frogs and I was thinking I will probably use alot less water than i will with keeping fish, I should just use distilled water i buy at the store to mist my tanks with but would like to know if i'm going to using alot of water.

Are RO systems the way to go? are they easy to install? The misting system will only be hooked up to 1 tank so would it be worth it?

My main questions are : How many tanks are you running, and how many gallons of water approximately do you use? How often do you mist a day and for how long?

Thanks!