My top level relations:
* Fun: Sex, drugs, rock & roll
* Home: Rent, buy, interior, yard, cars, places
* Meta: This system
* Mind: Philsophy, language, math, art, music, science
* Money: Accounts, investments, Bitcoin
* People: Family, friends, everyone
* Self: Fitness, health & illness, spirit, food, fashion
* Tools: Computing, devices, productivity, maker, crafts
* Work: Career, job
Roget's original thesaurus, which divides every word into 6 (or something) top-level relations was also an inspiration.
These are my root items in Workflowy (with its infinitely nested bullets).
I star active projects so they show up in the sidebar. I shift-drag (to mirror) items out of projects into the root (above the relations) to serve as my daily todo list. All in all, simple, efficient, and comprehensive.