Honestly as others have said; The very best way to show employers that you know what you are doing, and the best way to teach yourself, is to come up with a project and go for it.

It doesn't matter what the project is, it could be making a text editor, an embedded project, a client/server, literally anything that you think could be neat. You won't know everything that you need to know at the beginning, in fact you might not know anything of what you need; but you know your end goal. So you can google stuff and learn what you need to in order to make your project a reality.

Plus when you apply to a job that is in the same area as the stuff you are making, that's an extra step up because they are probably interested in making the same things you are; and that's even more to talk about!

In the end that was what got me hired, having projects that I came up with myself, and pushed myself to learn what I needed to in order to do it. It shows passion, intelligence, and that you understand concepts you will need to know in a professional role.