Leveling is mainly for the ability trees. You get stronger by collecting Essences. They're found in higher quantities in deeper floors of dungeons, and some dungeons drop more than others. In the meantime, take advantage of the fruit tree (next to the Sewer entrance), the town slime (the purple dude near the front gate), and the workout weights (behind one of the buildings in town). Experiment with different weapons, too. Status effects aren't particularly fair in this game.
Don't eat Essences as you pick them up, either. Go to an apothe-christ and get them converted to the stat your weapon is using.
Also, find companions. Some are stronger than others.