Gold is what you earn in the game. It is one of two currencies in TombQuest. You use it to buy monsters, traps, and more. All things in the shop, except for treasures, are purchasable with gold.
You can get gold by raiding tombs or by your tomb defeating raiders. If you break a clay jar inside someone else's tomb, there is a chance that it will drop a gold coin. Additionally, defeating monsters will drop a certain amount of gold that you can pick up. If your tomb defeats another person, you get a reward in gold. Take note that removing items from your backpack does not give you gold.
Gold is connected to the gold in Spirit Animals, so you can also earn gold by playing quests, selling items, and other ways you would get gold in Spirit Animals.