Ugh, where do I begin with this one...
You have the same problem that a lot of us have had when starting out music. You have the tune and the final results in your head, but not the mixing quality nor the ability to choose the correct sounds. And I feel the pain too, because the melody (just taken at face value) is sorta kinda catchy but sorely needs something to back it up.
If you had this idea in mind when you were three, imagine what children's songs would be like. Full of punch. Heavy on the instrument layering (unless this was Teletubbies or Sesame Street). Really good chords and a feel-good atmosphere. I mean, you're feeling my description now, aren't you? -- Trouble with this particular song is that the synths are tinny, the drums are flat, and there's nothing to give it excitement. And it's so empty.
I wouldn't want to give too many tips at once, but at least start with this one: Build up some chords. Make progressions. See how they sound. Experiment again. Keep doing it until you wow yourself, and then do it some more.
If you insist on this being drums and voice, make it sound real -- like, you know, those rap songs, or those medieval rounds which only have drums and voice. If you're not sure where to find voices, there are a number of us on NG who wouldn't mind helping you on this, if you should only ask.