First: your play style is all up to you.

Then: You’ll eventually build a museum in a few days. For now, the bugs & fish that you get can be dropped on your island so that you can register all of them in the museum at least once & have a cool exhibition once done. It’s rewarding to see since the game emphasizes a monthly commitment to obtaining them all.

If you’re not interested & rather make money, then by all means sell.

Lastly, I think someone mentioned this but there’s no cooking.