Catch anything and everything you can and bring them to Tom Nook until the museum opens, then continue stockpiling new creatures to give to Blathers so when the tent opens, you can get the museum built right away. The museum is AMAZING.
Also, hunt tarantulas on a Nook Miles island tonight and sell as many as you can ($8000 each), then buy a crap ton of turnips tomorrow before noon to sell during the week for a substantial profit. If you search tarantula hunting on Google that will show you the way. Basically, any flat island and you’re golden. But you can still get them with various multi-tiered islands.
Once you upgrade your house you’ll get Nook Miles. Focus on completing as many of the Nook Miles + items as you can each day. You’ll use Nook Miles for purchases more than bells.