I am a LaTeX newbie. I am curious to hear your recommendations about the best places to learn it. More precisely, I am going to start writing my doctoral thesis in it. Our school already has a template but I would like to get the basics first before diving into that template. With that, I plan to continue writing my journal articles in LaTeX instead of MS Word (which is, as you may relate, sometimes painfully unfriendly to scholars when it comes to formatting).
My go to is Wiki. It literally has everything you need. It is laid out pretty great where you can both learn, and use it as a reference. I use it often. Also, the TeX - LaTeX StackExchange is an excellent place to get answers to specific problems.
Once you have an appropriate template, this will give you everything you need to format your thesis. Good luck!
Also, don't bog yourself down with the details (in my opinion). Understanding exactly what the LaTeX code is doing is going down a rabbit hole. Just focus on understanding what you need to do what you want.
Little known fact: arXiv is great for this. Look for papers in your field on arXiv, and instead of downloading the pdf, download the source file (changing the file type if needed, so that it will open). Not only will you learn how to make fancy tables, pictures, etc... --- you will also often get to read all the comments that the authors neglected to remove before submitting their paper.
Once you are underway, learn features as you need them.
Ask questions on this site.
For a large project like your thesis, check out the workflow tag. You will find strategies for working on one chapter at a time by setting up a good file structure and naming conventions.
@Shinobii is right to warn you not to try to understand too much about LaTeX innards. You will probably never have to read what's in the university thesis template.