Don't do machines, they are really not that good for most uses. The fringe usability I can think of - competition bodybuilders, training around injury of professional athletes. That's probably it. Anything else ain't worth it.

People often do max 1 specific muscle with them, ie biceps or chest to impress and fight low self-esteem, but that's generally not a good way either.

As mentioned, muscles work in complex groups, and having 1 part way stronger than the rest will lead to injuries in real world usage. And injuries mean you will lose it all, and possibly worse.

This.

P.S. Love your username. You'll be pleased that the name of my garage gym is the Gravity Chamber.