I was a child of the 70's and did so many of these:
I made my own library by making little paper pockets inside my books and making the little 'slip' of paper where you marked down the dates
I made a supermarket by spending weeks / months collecting the empty packaging of our household things - cornflake boxes, coffee jars etc. I pretty much had an entire range! We had a toy cash register and a toy trolley
I spent many many hours making houses and families to go in them out of plastecine and a cardboard box and old scraps of material
I wrote books in copy books regularly
I used my much longed for tape recorder to write, act and record plays with sound effects (clopping horses, creaky doors etc)
I collected ladybirds in matchboxes
I collected scented erasers or rubbers as we called them
I roller staked (over the shoe type)
I rode my bike for hours
I climbed a lot of trees and built dens
I made outfits for Sindy out of old socks - very inventive!
I drew lots and lots of pictures and when a bit older (very young teen) I collected 3 series of a magazine 'How to Draw' and the binders to put them into by threading little tabs into the staples on the magazines. I revered those magazines and used them a lot and I still have them all now on my bookshelf. They were an indulgence for me at the time and I knew it and was appreciative.