Honestly, if you’re on a path (freeCodeCamp or otherwise) I think it’s best to search for resources as you need them. You won’t know ahead of time which areas you’ll need extra resources for or what sort of resources work best for you. I wouldn’t worry too much about trying to build up a library in advance. Just get in there and get your hands dirty. When you have a challenge that doesn’t make sense, break out the google-foo.