A lot of people use shoe racks to store filament. The one linked below from Amazon is inexpensive, but the dimensions are not quite right for spools and the included plastic braces are too flimsy for the weight of filament. This redesigned brace lets you build a custom rack which can accommodate both full sized spools and mini spools. 

https://www.amazon.com/dp/B0F1FMG887

You could also use dowels or any other 10mm cylindrical object, but I haven't found a source that's better priced. Assemble in the same manner as the instructions tell you to, but only use three cross braces per level. This extra space will give you a spot for full sized rolls. If you want to store mini spools on that shelf, use all four braces. 

The 3mf includes a version with a compound dovetail so it can be printed on smaller printers. Use a good adhesive if printing this version.