I divide mine up by general topic, and then divide each runtime up by specific figures:

I.E. --

Character Runtime

     - Pose
         - M3 Characters
         - SP Characters
         - V3 Characters
         - V4 Characters

.....etc.

Clothing Runtime

       - Figures
             - M3 Clothing
             - SP Clothing
             - V3 Clothing
             - V4 Clothing

......etc.

**Hair Runtime
**
Equipment Runtime (subdivides into sci-fi props, vehicles, weapons, tools, etc.)

Environment Runtime (includes outdoor scenes, buildings, rooms, etc. -- plus furniture)

Working Runtime (for special projects or items/characters created for specific scenes)

Misc Runtime (for those occasional odd items which defy classification)

......and so forth.

Also, under each category I break off separate folders for free downloaded items vs. commercially purchased items.

Total number?  I'm not sure.  I'd have to go home and count them.  Probably around a dozen -- each with much more detailed sub-folder structures.

Something To Do At 3:00AM