Once you get the hang of it, you can win like 95% of the games.

In the first ten levels, starve yourself and only eat at 30% hp.
Use corners and other obstacles to your advantage to get sneak-attacks. Don’t equip any unidentified equipment if possible - especially if it is suspiciously high level for the area. It is probably cursed. Save up your upgrade scrolls until you find some tier 4 or 5 weapons and armor. If you’re a mage, just dump them in your wand of fire from lvl 1 with no regrets.
Learn how the bosses attack. The slime hits really hard after charging, so figure out how to dodge or get out of range.