This is all good advice. Compose is a loaded term but I'm assuming you're talking about composing electronic tracks. (If you're talking about composing classical music you really need to go find a comp teacher. Not an online course, a real human that you can interact with.)
I think if you want to write some cool tracks you really just need to start writing tracks. There's not some step by step program you can follow where you do little exercises and when you're done you write the best tracks ever. A world class violinist doesn't learn to shred violin by reading books or blog posts, they become badasses by playing violin every day. Learning the tools of electronic music isn't any different. Music theory can be helpful in getting ideas more easily out of your head and into the real world but I don't think it's completely necessary. Use your ears. Just find whatever kind of stuff you like and write a track like that. Listen to music with an analytical ear. I'm not saying make a direct cover of a track you dig (although that isn't a terrible idea, especially if you're starting out with no experience), I'm saying find a track you like, figure out what the basic elements of the track are, and then make a track using those elements.
For example, if you like BoC, lay down a hip hop beat, throw some warbly ass synth lines on top, and sprinkle in a some sampled kids voices. The track will probably be shit, but the experience you gain making the track will be super beneficial for future tracks. I wouldn't worry about being original, eventually your music will become the sum of all your influences (all the people you choose to rip off) and that sum will be unique.
There aren't any shortcuts. If you want to write good tracks, just write a lot of tracks.