OPT:
1). Sell everything at harvest time, or in the bulk anyway if you're having trouble finding enough stuff to pay for it. Remember to make sure you have at least five! Find lots of wood cut into pieces then put them in your inventory.
2). Then it gets moldy and crumbly, and will gain a shiny seem. Complete the quest " wanting to raid sorn's castle by dinnertime? ".
3). As an alternative you can ship it back to the coast where you can get a bigger reward. Sell your loot to the senegal.
4). Keep doing this until you've sold every shell and all the fruit on the ground. If you find a coconut, plant it.Choose from options above and answer: What most naturally follows?

How to earn bells on animal crossing without time travelling or hacking
Collect a lot of shells and fruit.
Get coconuts that have washed up and fill your inventory with everything you find. Sell it all.
Answer:
4).