One thing I’m finding helpful in my experience with JUCE is that it’s really important to have a good handle on C++ as a language.
I know that sounds like stating the obvious, but so many things that I’ve been seeing in helping others through The Audio Programmer (and in my own experiences) is that many of the difficulties arise from not having a good understanding of the language and it’s data structures etc.
I’ve found this awesome course that had been really helpful for me, and I think if you’re committed to really learning how JUCE (and C++) really works you’ll find it to be a nice supplement.
It’s called Design Patterns for Data Structures (Pepperdine University) and it goes through many of the fundamentals of the C++ language- inheritance, pure virtual functions, object oriented design, algorithms, abstraction etc and takes you step by step through everything.
Available for free via ITunes U: https://itunes.apple.com/us/course/data-structures/id546468797
Hope this helps others as it has for me