Part of it is that you should preferably use things you already own (like books, craft and art meterials) or have access to - library books, online resources, like free courses, the internet in general, videos. There's tons of video courses on YouTube. And if you're an Audible member, check out the many Great Courses audios in that are in the Plus catalogue. (Or maybe on Spotify if you get audiobooks there.) You can do loads without spending anything.