I've not see any decent discussion or analysis on how your score is actually calculated. I can't seem to find any parameters in the xml files that would give hints as to how to 'optimise' your score.
It's much easier to 'optimise' now by just submitting a bogus score to the leaderboards So if I wanted to 'cheat' cheat it would be fairly simple to do. Mostly just looking for high level kinds of things that impact how the score is calculated. Do total turns taken count? Potion/food usage? etc.
I am sure it is more complicated, but the best answer I've come up with is "exp gained". Sit in a small room on floor 10, spam space for 10 minutes, clear dungeon for 1m exp, repeat.
Gaining levels OR experience, drastically increases the score. I changed the mobs on level 1 to give 99999experiece on death,so I can have a look at various high level spells and after 35-40kills i reached level 35. Died on purpose and had a highscore at the 40.000.000 range.