Auto-battle
After completing a level out under the easy difficulty setting, try it again in normal and hard with auto-battle active. In this mode, your character will automatically make their way to the Boss, defeating all enemies en route. The higher the difficulty, the better the rewards.
Upgrades
Reach level 5 to unlock the forge. You can spend materials there to craft new equipment. Crafting is the best method to obtain new equipment and weapons. Combine four pieces of outdated equipment to create a better piece of equipment. The higher rarity of equipment used, the better the result. Note: Fusing equipment may cost a lot of gold depending on what you are trying to create. At times it may be better to sell old equipment.