Idea on economy make-shift bookcase?

Hi Betty, Your question reminded me of my college days. We used cinder blocks and 2 X 4's to make bookcases. Just stack the blocks and put the boards in between. It comes down easily to use somewhere else or even recycle the blocks and boards.

Utilize a board with a cinder block or brick base; crate; shelf; wicker basket; hanging wire basket for small books

Oh yeah, I've used cinder blocks for years. I don't see a need to use 2x4s, though. 1x6s or 1x8s would be sufficient unless you plan to put something really heavy on them.

I used the cinder blocks in my first apartment. You could also use books stacked at either end of a board, then add more books and another board. Just level them up according to thickness and use less used books for the upright portion under the boards. This makes them less accessible, but still available if you really want to read them. Another thought is to use large tins (like the ones you get at Christmas with popcorn) as the supports for the boards (no more than one high between the boards).

Two file cabinets, one on each end and a old door to span the distance in between.

Stacked wooden crates, milk crates, if you are allowed to attach screws into the wall you can head to a building store and pick up pipe flanges and attach them to the wall to get this look... https://www.pinterest.ca/pin/530158187367504749/ there are many variations so do a search if you like this idea!

plastic milk crates stacked on their side