Basic things I should know about

So I just kinda got into this stuff and honestly it seems fun and I would love to do more. Ive heard about casting sand and I don't really know what would be good to get, preferably get reusable. I've been possibly wanting to make rings, handle's, anything I can in the casting sand and I don't really know what else I may need equipment wise. Any help would be great since I don't want to spend a lot of money on screw ups or things I didn't need.