Slumdog Skillionaire: my secondhand XCD ski quiver explained

Looking to XCD ski on a budget because your wife keeps having babies or you’re still waiting to land your first grown-up job? Here’s a resource to help you recognize what gear to keep an eye out for depending on what kind of skiing you want to do.
Feel free to ask for more specifics about any of this gear.
Also, I think I used cable/spring in the wrong way when referring to heel attachments because those terms don’t match what you feel like you’re looking at when the gear is right in front of you.