Quite uneducated but trying

[DeProgrammer]

So I'm primarily a coder, but I like to mess around once in a while and make pixel art, sound effects, and music (so I'm essentially a complete team and don't have to rely on others too much for my hobbies). At the moment, I'm trying to improve at making music so I can come up with something good for my current project. Once I improve a little, I intend to try to creatively mix some recognizable parts of Metroid music in an otherwise original piece. I'm aiming for a space-y feel, of course.

Anyway, this is a proof-of-concept piece I wrote last night. (That's a MIDI embedded in a blank page for technical reasons.) I'm artistically stupid, so I'm having trouble picking out what I should do next. Anyone wanna tutor me a bit?

Oh, yeah, about the topic title... I've never taken any sort of music class, I don't play any instruments other than a few simple pieces on the piano, and as I said, I'm artistically stupid. But I have read a few things about music theory a couple times, and I've made about 40 pieces that I (somewhat) liked...but it's never quite what I'm looking for, always too short, and rarely "finished."

More info: I use Anvil Studio to make MIDIs. For my game, I need to make IT or XM-format modules, which are easy enough to convert MIDIs into. I also have a nice collection of instrument samples at my disposal. I do not, however, have anything that required money to obtain legally. Either way, I'm hoping to get better at designing music, so the software should be mostly irrelevant. (Pitch blending isn't necessary for a melody, after all!)