That is just plain dumb, just ask a girl, don't do any creative shit. You're already going to spend a bunch of money on the bitch, just fucking ask her. I doubt it will turn into any meaningful relationship anyway. I know, how about you be creative and just ask her, nobody does that anymore, maybe she will appreciate the simplicity of it, you know without and childish little games. Oh wait homecoming is just childish bullshit anyway, maybe you should come up with some grand retarded plan to ask her.
Secondly, you don't deserve a plan unless you come up with it yourself, what would the girl think if she knew you just asked a bunch of 14 year olds on the internet how to do it??? She would probably think you are a douche nugget.
Thirdly, I have noticed a correlation between the way a kid asks and how well the dance/relationship is.
The more games, and "creativity," (if you can stoop low enough to call it that, since you yourself didn't even come up with it.) you use, the worse the dance or relationship goes. In the end it doesn't matter at all, you might feel all good about yourself but it's just dumb.
So I suggest:
1. Don't go, don't worry you won't miss out on the hs experience, because it is bullshit anyway for the most part.
2. If you insist on going, just ask her in a simple way and go on with your day.
Anyway, I hope you have fun at homecoming.