I organized my "project sorting" plastic shoeboxes last week. I have pretty close to 30. About 3 empties ready for small bins projects to grow into.
I start with the smallest bins Dollar tree has, about 3-1/2 x 4-1/2, then 4x6, the third size holds two of the smallest in it side by side, so it's about 7 x 4-1/2. It will hold 3-1/2 x 6-1/3 bricks. When the quilt being cut out outgrows that bin, it goes into a shoe box. When I start making blocks, if they are larger than 6-1/2", they graduate to a flat bin or lidded bin.