Are there any courses that focus on creating an impressive end product for my portfolio?

An impressive reel is original, not examples from some course or a re-do of a bunch of tutorials. Something original is about only about 10% what you may learn from a course on how to use the tools. The rest comes from immersing yourself in every other aspect of the art you are pursuing.

For a killer visual effects and motion graphics reel, you need great design skills, a good understanding of principals of animation and a solid background in color, composition, light, and shadow, a good understanding of how the human eye and brain react to motion, color and sound. Just knowing how to push the buttons in AE won't get you very far.

A rehash of a bunch of other folk's work might get you a couple of jobs as a technician, but that's about all. There is no sure-fire way to build a sample reel that will have the phone ringing off the hook. You only get that by producing real quality work on time on budget and reliably so the folks that have the money to spend will recommend you and your list of credits is expensive. Winning some big award will get you a couple of jobs for a few months, then the excitement will die down because you are only as good as your last job. 

Don't be discouraged, just roll up your sleeves and get to work learning and experimenting. Knowing how to push the buttons and throw the switches in any software is only about 10% of the knowledge needed to be a truly successful craftsman. If you work your craft long enough with enough skill, maybe someone, somewhere, someday, will call you an artist.

Your question is the answer: made up your mind for an impressive AE project and start doing it.

Everytime you stuck, think about how to solve it, search online and ask in the forum (in this order!).

Hiring companies and clients don't what to see a version of a tutorial you watched on yt. They want to see something from you.

Be original, have an idea - don't mind how to do it. You'll learn on your way through.

At least, that's what I do since I first opened AE eleven years ago.

*Martin