I have a good system:
Use Folders on Google docs. I have files and folders about literally everything. And Google docs is pretty comprehensive in terms of being able to create TODO lists and everything.
Everything I commit to doing in my life is worth writing about. For example, I've been learning German for a long time, and keep a log of what I do, and new action items or things I need to improve next.
Docs is accessible everywhere and easy to use.
I believe that for this, you don't want a tool that offers too much functionality, they take out the pleasure of writing things down.
While writing things down, I learn a lot. My ideas are organised. I don't want a tool that gets in the way by showing me how many TODOS I have, stats or any pointless thing, or that it looks gorgeous. I want something functional, so my focus is to organize myself.
I also keep my finances organized in Google sheets, as you can run scripts on it (even regular scripts, to create aggregate data).
It is incredible how much one can do if they explore the full capabilities of those simple tools, instead of looking for a shiny thing that can do for themselves.