For any CSS newbie I would encourage them to learn Flexbox and Grid. I find that layout is the most confusing and those two display modes have greatly cleaned things up. It’s amazing how much they behave the way you intuitively expect them to. They eliminate… I’m going to dangerously say… most newbie gotchas.

Beyond that, 100% in agreement. There’s just so much and when it all interacts it can be a nightmare.