I fold Large yardage of fabrics around my 6" ruler slide off and stack on the wide wire shelves in my closet.

For smaller pieces I wrap around the same ruler. Smaller amounts goes on top shelf.
Larger yardage goes on bottom two shelves.

Nothing to buy.

Comic book boards.. I bought some years ago and wrapped fabric around them to store,
Ended up giving them away..I guess if you have a bookshelf to put them on it would make sense...the heavy cardboard could also be used for making stencils.

I use these too. I went to my local sign maker stores and bought scraps that I could cut into the sized that will fit on my shelves.

For those who use foam core or Coroplast, if you have a convention centre in town you can probably get as much as you desire for free.

I was the signage volunteer for Quilt Canada and the event organizer told me the signs are usually tossed at the end of the event. She was amazed to watch me walk through the remaining attendees and give away all the used signage. I was flogging them as mini design walls.

I get the carboard from Joannes and cut it then wrap my 2 - 3 yrs on them and they stand up like books onthe shelfd.
I love it.

I use foam board from Dollar Tree.

I used cake boards from Joanns or Michaels with coupons and cut them in quarters. Use them for 1yd. Or more fabric lengths. My FQ I store in a CD bookcase.

I have a friend that just has it all folded neatly, on end, in an antique dresser.
I have large (4-6) yardage wrapped in think cardboard box I've cut and stand on end, some folded flat, and small FQ and under in small bins. Works for me.