First of all, fun song and improv :) I enjoyed it! As a fusion-improv performer myself, I totally understand entering the stage without a clue as to how the performance will go. You did great :) Loved your song and costuming choice!

The only improvement I would suggest is to be careful what you do with your arms and keep your posture throughout the performance. I know arms and posture can get lost in the shuffle when you're trying to think on what movements to put where to accent the music, but definitely something that can really strengthen the performance if done well. Not to say your arms were bad or anything like that, but I have a tendancy to forget where my arms should go when I improv so I'm conscious of them when I watch others!

On how to prepare to improvise...one thing I do is to listen to the song several times and really know your accent points you really would like to hit if you can. Maybe practice a little to the song so you don't have to really think about what section is coming up next. You don't have to choreograph anything, per se, just get really comfortable with your music and the improv comes much easier, in my experience! Hope that helps and again, good work :)