Birdwatching. You can buy a book and binoculars if you like. The app Merlin is somewhat free to ID Birdwatching calls. Birdseed can get expensive or just plant sunflowers.

Wildflower identification. Best in early spring, Phone apps make this a little too easy. Seed collecting and propagation is my next goal. I also pull up invasive plants, mostly garlic mustard.

Gardening. Seeds are cheap but if want to start indoors you’ll need a light and possibly a heat mat. Start outdoors in a makeshift “greenhouse” using a clear plastic jug. Starter plants are cheap