Try to use the salk market which means buying turnips from Joan every sunday morning (Guide Here: https://www.youtube.com/watch?v=5tDVqbf2fvw ) Also if that's not your style you can go bug hunting on the island after 7:00pm. I'd recommend going after 9pm because that's when I find that sharks come out more often and the Ocean Sunfish which only sells for 4,000 bells goes away (Guide here: https://www.youtube.com/watch?v=ZVAWlQFPPRM ) Those are the best was of making fast money. let me know if you need anymore advice!