Hello, James. Welcome!
You can start with the FileMaker Training Series:
Other resources include:
As for the "'best' place to learn how to be more effective", the question would be: How do you define "effective"? And what is your learning style? Do you prefer classroom, video, or reading? Would you rather learn at your own pace, based on accomplishing a specific task, or do you like more structure?
My own preference is to lay a good foundation of basic principles, then move on to "how do I do ...?". However, many of us learned by trial and error over the years, building on what we already know. (Of course, many of us also entered the FileMaker world decades ago, when the product was considerably simpler, so that does factor in.)
All that said, by all means, dig in. It's a wonderful world!
If you have 14 or 15, you can look through this file as a "fun" project. It's not great for demonstrating typical data management, but it uses lots of FM features* you'll end up using in practical applications.
(sorry community, here it is again ...)
* - note that repeating fields should rarely be used - mine are for display purposes.
As well as the excellent suggestions above Google "Database Normal". You'll find a lot of useful database principles.