First, you go to Ezra on Predator's Paradise to get the shovel. Now you can dig about on the beaches to get items to sell to Ezra. Next, you want to go to Holly, and build her relationship up to at least 30. Once you have done that, you can go to a beach, dig up stuff 3 times, go to Holly for some milk, and repeat. You can get up to nine items during the day easily. Usually, you can get at least 100$ worth as long you get more than just half digested wallets.