well, dont bother with all the assholes on this site, you start to just ignore them. Sounds to me like you are about 12-14 years old, not trying to be mean, just saying this because that means you are gonna be growing fast and soon. so you are gonna want to get a ski that you can use for awhile unless you plan to buy new skis every year fot the next few years.
SO with saying that, you are not gonna want to buy a twin tip under 160. at your height a 160 would be perfect, but your still a lightweight so i wouldnt recomment going anything over a 172 because they would be hard to control.
Where do you ski? and how long have you been skiing? Depending on how agressive you are, and taking from what you said, seems like you havent really ever been skiing, but thats ok. So i would suggest getting something around 160.
Also sounds like money is gonna be an issue, so at the time try looking at getting a pair of last year skis, you can get a great deal on old stock and there are always tons of left over skis in your size. I wouldnt buy a pair of junior skis because you will realize soon how much they will hold you back. So i would suggest looking into either a pair of Line 1260's, 1080's, or fugitives. you can get any one of these skis for under 350