In addition to the above comment i made and in line with other comments. If the image file stays under control of Lightroom, there is little reason to separate the storage into several different folders (The bucket approach described in The DAM book). However if the derived image(s) (f.i. an export to JPG etc) is(are) not under control of LR (not added to the catalog), then i use a folder for derived results. As i work per assignment or project if you will, my basic folder structure per assignment is: <Assignment>-ADMIN, <Assignment-EDIT>, <Assignment>-DERIVED
The ADMIN folder holds any assignment administration related files, like model-agreements, moodboard/soryboard, etc; the EDIT folder all the image files imported from cameras and any files created when going to Photoshop (LR stacks these by default), the DERIVED folder any derivatives not under control of LR, f.i. created with export command and not loaded into the catalog.
I use keywords extensively, and smart collections in combination with regular collections to manage my image development work the selection by customer and output per assignment.