How to make a good martial artist?

[CharonsHelper]

plus a ring of ki mastery brings the cost of ki powers down by 1, minimum zero

I totally agree - except for this. The Ring of Ki Mastery says specifically "As long as there are at least 2 ki points stored in the ring, the wearer reduces the number of ki points needed to use a ninja trick or ki ability by 1 (minimum 1 ki point).".