There is a point in time in your learning process where you'll realize this:
You have the knowledge you need to start tackling the idea you have in mind.
Having a personal project you care about is the best motivation to overcome the obstacles that will inevitably come into your way.
I'm a heavy podcast listener, and I especially like episodes where some person describes the journey from zero to having a product online. Many times, the person starts from zero knowledge and builds the skills right when needed. Not before, not learning too much stuff in anticipation, just doing.
How do you solve the problems you'll step into? Using Google of course. Google is your best friend. I've been developing professionally for 10 years now, and I've always used Google and Stack Overflow to answer my questions.
But Google is just a tool, a dumb machine that will match pages to your keywords. Stack Overflow is just a web application that would be useless without the people that spend lots of time answering questions on it.
Behind those sites, there are millions of developers that took the time to write some blog post or answer a Stack Overflow answer.
I am one of those people that share information on the Internet, as I write one tutorial per day here on this blog. Since I've started, I've written more than 300 tutorials. Let me tell you this: you will never stop reading tutorials, ever, because the tech changes constantly.
Something that everyone uses today will be considered legacy 10 years from now. It's happened before, and it will happen again. Think jQuery or Angular 1.0 or XHTML.
Also, your needs change constantly.
Something you learn today will be the base on which you'll build something cooler tomorrow.
But don't let learning stop your progress as a maker. The most important skill you can learn is not how to make the code do something, but how to make something with the code.
Build something you're proud of, and start today.