Aside from when I read The TeXbook, I have only ever used TeX for immediate problems. But, I have to familiarize myself with typography in general, for a job. I am finding the documentation in TeX Live to be helpful. But, are you aware of anywhere to find exercise documents?
I mean, example layouts which you would attempt to duplicate using TeX or anything else.
Using the package documentation, I search through it to see something that looks like it would be a good exercise and then try to duplicate it.