You can unlock the Auto battle option for a particular stage by first earning an "A" or "S" rank on it. level, which is done by completing the level under certain conditions. The following four conditions will determine your rank. Complete all four to earn an "S" rank or three of them for an "A" rank.
Complete the level normally.
Complete the level solo.
Complete the level under a particular time limit.
Complete the level without taking a certain amount of damage.
God of Iron bonuses
You will get three free offerings for the God of Iron daily. This will be a uncommon, rare, or epic item. If you offer to him enough times you will automatically receive a free gift. Otherwise, The God of Gold requires gems, the game's premium currency.
Launcher skill
One of your starting skills can launch enemies into the air. Use it as often as possible to make enemies defenseless while in the air and execute combos on them. The launcher skills usually have short cooldowns allowing them to be used constantly.
Upgrades
Spend gold to upgrade the slots of your character's equipment. They act as passive upgrades to your character. After you are at a high enough level, you can break down equipment to get upgrade materials.