I've built my deck around poison using this spells
The thing is that [poinson bite] adds X stacks of poison per stack already applied, so it build's up really quickly.
Spirit Break Spread all DoT stacks from target to all other enemies (yes they also stack), and dark flames increases dmg per stack of DoT applied, and everythingelse is either there for suvivability or for supporting the cards mentioned before.
After Beating final boss (it dropped [Ultimate Magic] ) and getting the neutral ending i've changed for a [focus] stacking build
The important cards here are [ultimate magic], [Psychokinesys] and [Rest]
[Ultimate magic] increases dmg and decreases cost for each stack of focus, Discarding [Psychokinesis] gives a lasting buff that gives stacks of focus on the begining of the round if you havent taken dmg (free focus on first round)
Every other card has cost 1 and a focus rune 3, UltMagic has splash, buff to main effect and double cast.
The rotation goes: Cast 5 cost 1 cards > Rest card > UltMagic > deals about 760 dmg to target and 90% to everything else
Anyway... Heres a Save, contains all memories, but i havent found all spells yet. Just slap the content of the folder in ...\AppData\LocalLow\FuusenHanabi\Take Me To The Dungeon!!