Spades are pretty useful in the game for farming and treasure trails that require you to dig, and can even be helpful in some questions. You can find spades in several locations, and the most common location you’ll look through at the beginning of the game is at farming shops and general stores. They can be bought cheaply, and you can also find them at your player-owned house. You just need to make a ‘tool store 2’ upgrade to your house and then you will have a never-ending supply of spades! Rogue kits also have them, but as said before at a very low level you will be finding them in farming shops and general stores.