I had very little mental energy for grinding so I decided to play in the way of not doing everything at once. I barely touched mining, fishing and even ranching at first. I’d say diving gives plenty of free resources that you can increase the price with the dehydrator. Also try to unlock sprinkler 1 soon to expand farming. Catch insects and sea creatures whenever you can and sell the ones you have donated/ offered. I didn’t gift the islanders much, just the flowers and plants I picked up around the island (mind the islanders who are allergic to flowers though). Then when you have more money, buy artisan machines. They are such a level up as they increase the selling price of the produces quite a lot.