At the Golden Hammer Inn on floor 1, talk to the dwarf that makes new rosters for your party. If your party is already full, remove some party members, but do not delete them if you still want to keep them and their items. Then, create new characters. Move the new characters to your party and unequip their items. Sell the new characters' items. Repeat this process for more money to buy better items. When you are done, delete all of the new characters at the starting screen and add your previous characters back into your party.