You pretty much always have to waste the starting spell. Your first 5HP worth of attacks is rarely going to give you enough information to deduce a path, so you'll need that sound 6HP to try to find another scroll.
You can't waste any heals if you want to clear the board.
I cleared the board multiple times using the exact tactic I outlined.
Wasting it is the same as just keeping it unused forever, the other use for heal spells.