~/Documents/gfx/working/ holds pretty much everything.
~/Documents/gfx/working/ . this year. alias of the appropriate yearly folder, named to sort first in the Finder
~/Documents/gfx/working/ big project 1
~/Documents/gfx/working/ big project 2
~/Documents/gfx/working/ big project 3 aliases to big projects, space-prefixed to sure ahead of the yearly folders
~/Documents/gfx/working/2019/
~/Documents/gfx/working/2018/
~/Documents/gfx/working/2017/
...
~/Documents/gfx/working/1999/2000/ Yearly directories. Big project folders live inside the appropriate year.
~/Documents/gfx/working/old big project 1
~/Documents/gfx/working/old big project 2
~/Documents/gfx/working/old big project 3 aliases to big projects I don't want to keep at the top of the list
There's some really old stuff a level up in ~/Documents/gfx/ but it's a remnant of a time when I had different ideas about organization.
I keep ~/Documents/gfx/working/ in the Finder's favorites sidebar, along with the . this year . alias and the aliases for 3-4 current projects. Makes it easy to get to them them through both the Finder and file dialogs.
Big projects have their own file structures within their directories. Usually it's a bunch of Illustrator source files with Finder tags to tell me what's been finished and/or posted to Patreon, and subdirectories for things like web renders, reference files, book production, ads for the project, etc.
General reference/inspiration stuff either ends up in a directory outside of this - maybe in ~/Documents/ebooks/, maybe in something like ~/Pictures/reference/ or ~/Pictures/random inspirational/, there's no solid system. Reference stuff can also go in Evernote depending on how I figure I'll want it.