What minimum or maxmum HP percentage for use potion when I use black spirit mode?

This is controlled Via your Settings -> Convenience
You can have it set to 30%, 50%, 70%, and 90% 

For black spirit mode, you want to be farming ~200CP under your current CP Level. Your Potion usage will be at an all time low and leaving it at 50% or even 30% in some cases will be optimal for your experience. you will save Money while making money.