1. Import foreign fruit trees for extra bells.
2. Press A repeatedly to speed up crafting.
3. You can make most islands you visit with a Nook Miles ticket into a "tarantula island" and get a bunch of bells.
This TikTok explains it well, but here's a summary: Use a Nook Miles ticket and go to any island that has bugs. Cut down every single tree, break every rock, and pull up weeds and flowers so that the island is basically just bare ground. Dump all the extra materials you picked up onto the beach. This will cause more ground bugs to spawn, which includes tarantulas! If you go with a nearly empty inventory, you can make hundreds of thousands of bells in one trip.