These aren't too expensive. $1.50 each (if you buy 10) at beprepared.com (an oxygen absorber pack is under a buck each).instead of buying expensive mylar bags and oxygen absorbers
Ally has awesome advice though, if you haven't yet, search for her posts for some great insights. She's obviously been doing this a while, and really has her stuff together.
Remember the 3 rule:
3 days without water, you die
3 weeks without food, you die
(there are a lot more, just can't recall them right now)
3 minutes without air, you die
3 hours without shelter, you die (but only in really harsh environments..so I kind of toss this one out usually)
Part of me wants to say you're too young to worry about this, but really, the way things are going, probably not.I'm 15, a young pepper ( not one of those childish litte kids. Lol). The only time I go buy stuff is during the summer, when I work. But every now and then I try to pick up some things from the store.
My guess is you live with your family in a fairly urban area. Your big challenge will be stocking up on water too. So something to consider.
Hopefully, your parents have firearms. If they don't, I'd try to sway them, but without being pushy. Do they share your ideas? Or do they consider it foolish?
If the latter, you may want to visit the threads on how to get others onboard. Mostly, don't put it as "doomsday" prepping, but more for short-term natural disasters or unemployment, etc.