As you collect more and more gels and diffusion, organization and storage becomes important. I store my gels and diffusion using the following two holding methods (as far as rolls go, those usually live in their original boxes).
1. Lindcraft Gel Packs: these have one pocket that holds gels (standard sheet size and smaller) and it rolls up and secures with Velcro straps keeping your gels in order and protecting them from handling. Easy to use by laying it out on a flat surface. I have three, one for the diffusion/ND series, one for CTB/CTO/tint series, and a third for theatricals (a.k.a. party) colors. Check out Gel Packs on the Lindcraft web site.
2. Expanding File Folders: For smaller pieces (it’s handy to have small pieces ready to go for smaller lights) I keep them in three accordion multi-compartment file folders, one for the Diffusion/ND/CTB/CTO set, and another for tints and theatricals. I label the tabs with the gel type so when I ask an assistant, “put some opal on the 150 and 1/2 blue on the 300” they can quickly find the exact gel needed. It does take some discipline to sort everything back to the right section after the shoot, but if you do it as you go, it pays off in efficiency in the moment of lighting. No more hunting for the right piece. You can find these in any office supply store and I found some plastic ones are pretty rugged. People who do theater usually use file boxes, but I don’t have that many small gels and I like to be as portable as possible, all my gels and accessories and extension cords go into a single duffel bag.
3. Another tip: write on two opposite corners with a sharpie the gel number. On the set when its dark and your in a hurry, you don’t want to try to figure out which gel is which. Writing the Rosco or Lee number on the gel will speed things up while lighting and makes putting things back much easier.