As a 90k person I use lucky board for the charms...now only heavy spenders have above level 8 charms as I see so it will be a long time for anyone not to spend on lucky board plus there is always good ninjas in there...i think every player that need charms or medium refines should power up on this event but still its RNG ..my group mate upgraded from 3 to level 7 charm with only 90 charms..so everything is RNG