Any time that you need more experience points, go to a stage that you have already beaten and grind for some experience and some ore. Gaining levels will unlock new goodies as well as boost your Freeblade's stats. You'll often find new weapons and armor too, which can be saved and used for specific loadouts.

It's generally best to auto-equip your Freeblade with a loadout before the level begins. However, if you are having trouble with a level, switch one of your weapons (or even both of them) to weapons that the loadout generally doesn't equip for you on its own. A change in weapons might just be the key sometimes.