I second this.

Precisely because you have no other reference points, you probably wouldn't even really notice the improvement afforded by upgrades at this point. If you're enjoying your bike now, just keep riding. Then, as you get more experience, you might start to notice areas that could be improved, at which point you'll really be able to appreciate the added value of any upgrades you make.

I fell in love with fixed gear on a $250 hi-ten bike. I rode the hell out of it, as is, for nine months before upgrading, and even after those nine months I didn't really know what upgrades I wanted and basically wasted money on a new bike that really wasn't much of an upgrade (for me) after all. After riding the hell out of that second one for another nine months, I had learned a lot more about bikes and about my own preferences, and now I can really appreciate the quality and custom fit of the bikes I build up for myself.