IIRC, it's just following the portrait ghosts as you suck them in so you're close, while avoiding the poison mushrooms they drop everywhere to deter you. The latter could be tricky since they're black-and-purple and thus aren't easy to see in the dark shadowy mansion interior.
Doing 80% of the ghost's max HP in a single go qualifies you for gold frames. The bosses(Chauncey, that guy in the graveyard who I can't remember the name of at the moment, Boolossus and King Boo) are timed for gold frames IIRC.
Link meets Fire Emblem in CYOA: The Legend of Elibe! Come read, and find out what happens! Click below!
https://www.gamefaqs.com/boards/468480-fire-emblem/80952015