I don't know if it is possible to be totally organized so as not to purchase the same fabric more than once.
I do have a large shelving unit downstairs that I TRY to keep my fabrics somewhat organized by color on.
Another thing that I found helpful when I went on a shop-hop was I had my background fabric already for a project I wanted to make, then I clipped the
salvage edge that gives you the colors that coordinate with that fabric and I carried that with me. I found this much more helpful and accurate than pictures on my digital camera because they weren't always true to color where the salvage swatch was.
I hope this makes sense and helps a bit.
Muriel