Well, I'm sure you have plenty of tips sitting around these parts... Hope it goes well
And remember, if you're not able to get it now, there's always next year, or perhaps you would try to save up your allowance (if possible) and see if you can buy yourself one! I don't see why your parents would have a problem with that; it means you've worked your way through doing the daily chores and you're finally able to get your reward, so to speak.