Reddit reviews The Watch Escapement

Alright. You're thirteen. There are tons of things you could start with. One of the easiest skills to start learning, and one that applies to many other seemingly unrelated processes is filing. Shaping parts with files is an art all by itself, and it takes a ton of practice to be good at it. Get some round metal stock and file it into other shapes. Learn how to shape the metal according to dimensions you picked beforehand as though it needed to fit another part. It teaches fine motor control and working by feel. One of my first metalworking projects in Watchmaking school was to create a pair of identical hand pullers by hand using a sheet of dimensions.

If you're going to design your own movements and cases, manual drafting and CAD is another option to start with. Things like OnShape and Google SketchUp are great places to start with that.

You said you know about the books, but I can't help but recommend The Watch Escapement by Henry B. Fried. It goes through all of the important geometry that makes the heart of a watch work. It's a step by step guide to drafting the escapement using common drafting tools. Once you finish the drawing you should have an extremely good idea of how and why things are shaped and spaced the way they are and how to replicate it in your future designs.