If you're somewhat confident in C++, why not just go ahead and create a small audio plugin? Think of an idea, and then create it. Even though it's great to be a skilled programmer before starting projects, it's my experience you also need apply your knowledge before it becomes meaningless just to code.
I had some previous years of experience coding before i started creating audio plugins, but i quickly became frustrated spending over 95% of my time managing sources, projects, compilations, gui etc. etc., and only 5% actually writing DSP - this was pretty demoralizing for me.
After giving it some thought, i started a huge project which basically was an audio plugin that functioned like an IDE. It is a wrapper around a compiler, console and a texteditor along with a simplified api and a crossplatform model, that allowed to write only relevant dsp part and let the plugin handle everything else. You can then compile, run and test it on the fly inside your daw of choice. That allowed me to suddenly write lots and lots of dsp code, learning much quicker and spending much more time on doing the interesting part.
It's beginning to sound like an advertisement, so i wont post a link for it here, but you can PM me if you want to learn more about the project.