or...do the official Apple course!
2 UK-based courses: Soho, AcademyClass.There are many better guides than this online - the software is used by millions, so you won't struggle to find sites and YouTube videos dedicated to all elements of FCPX. I've tagged multiple posts on Final Cut.
If you get stuck with a technique or effect, or just want to explore further possibilities, have a look at sites like...
Apple provides a very clear guide: https://help.apple.com/finalcutpro/mac/10.2/. (I've included the full link as you can see you might need to check for an updated version)This vodcast draws on many basics you'll need to get started, combining screen recording, screenshots, a voiceover and frequent titles. You can easily skim in YouTube view to find specific instructions, following the titles.
You can also get an Apple manual.
I made it using Quicktime's built-in screen recording, allowing a choice of fullscreen OR dragging around a smaller area (I did both, depending on the element being considered, adding fullscreen and partial screenshots too).
There are many books (most including downloadable content for practice editing) you can choose from - here's a UK Amazon link.
Some offer free updates as the software is updated.
There's a lot of competition for your money (and many free video courses, see links above):
OFFICIAL APPLE COURSES, QUALIFICATIONS etc
Apple of course provide resources on FCPX. You can take qualifications in FCPX - extremely useful (at any level) for CV, UCAS and job applications.
If you look at Apple's main FCPX link, you'll now find some new tutorials with free downloadable content for practice editing in advanced techniques:
It's not hard to find video tutorials on YouTube: