Faux Fur Throw Blanket, Ribbed Thick Cozy Striped Fall Blanket,Luxury Plush Decorative Ultra Soft Fleece Blankets for Bedroom Living Room Bed All Seasons Overnight Home Gifts Sofa Indoor

You kind of sound like a young person, and that would typically mean not a lot of budget. I would probably staple fabric to cover the underside of the stairs. You could use an old sheet and old blanket - something that looks cool from the Goodwill. Wash it first dry it really well and then you can staple away. I like the lights and the most people I know that need sensory breaks would like that too. That said it’s super overwhelmed. It might be hard to find the calm ones easily. For the floor, maybe something like this https://a.co/d/00Fvu67E