In each town in THE DOG Island there are two shops: a consumable item shop and an accessory shop. The item shop will sell different tools, such as Medicinal Herbs and Potan's Medicine. Depending on the area, some item shops will sell region-specific items like Really Cold Ice Cream in hot places or Hot Drinks in cold places. In Rune Village, you can find Anc Water.
In accessory shops, you will find hats, glasses and other wearable items that you can equip from the menu. Each town has its own items you can only find there, but some items can be found in multiple shops around the island.
In order to buy items, you must have enough Woofs, the currency of the game, to purchase what you're after. Item prices can range from one Woof to over ten for some fancy accessories. Throughout the game, you'll earn Woofs by completing missions and selling collectible items to the different Collectors. Each Collector will accept either flowers, food, fish or bugs and will give you a Woof for each one once they have it in their collection. Collecting items and selling them is the best way to get enough Woofs to outfit your dog, since you won't earn enough from missions to buy everything.
You can also use Woofs to pay to stay an an inn.
One other use for Woofs, besides buying items, is paying Boris when you want to warp somewhere on the island. Boris charges one Woof per warp, and unless you like spending a lot of time traveling on foot, a good portion of your money will go to him.