Magic Tricks

Cost effective is a good boundary especially for a 16 year old.
Assuming that you'll need stage magic 'stuff' to address the larger audiences and you want to keep the budget in 'check', let's start here.
At PM, it's called 'Surprising Dots'. I've heard it referred to as 'Hoppin Spots', 'Magic Dots' blah blah blah.

http://www.penguinmagic.com/p/S15511

Easy to learn, inexpensive, visual enough for your stage, everyone thinks that they've figured out how you do it, and then are surprised when you explain the technique only to trick them at the end. Lot's of YouTube presentations to help you develop your own or 'borrow' one you can perform.

Also, for this age group, I like the 'jumbo' card routines. However, they can get a bit pricey.
Three favorites are:

Jumbo Card Problem (Vanishing Kings)
http://www.penguinmagic.com/p/6123

Jumbo B'wave
http://www.penguinmagic.com/p/S14110

Rainbow Monte
http://www.penguinmagic.com/p/S21755

Although 'out of stock' here, you can find these online by going to the authors site (Vladimir Magic for Vanishing Kings) or doing a quick search on the web.
Plus, you'll generally save money.

Or, a Yoshino Gimmick (cheaper ones all over the net i.e. knockoff)
http://www.penguinmagic.com/p/S838

Again, check out YouTube for some performance ideas.
Good luck with your show.

Learn the Linking Rings and some good rope magic. These will serve you well the rest of your life for stage and close up.

Put the keywords in the search box to see the variety that Penguin sells.

My son and his friend have done a few magic talent shows--they did the Peanut Butter Jelly switch, a torn and restored newspaper (the "no tear" one from Mark Mason that you construct, but only have to do it once), the "disappearing magician" where one steps behind a large trifold stand that's adjacent to the edge of the curtains, leaves a hand on one side of the stand (but it's really the hand of an unseen 3rd friend who is ducking behind) and while the first kid is still talking about the history of the great magicians (or whatever), the first runs behind the stage and down the hall, and pops back into the auditorium from the back only a second after the hidden 3rd person pulls his hand away. Light swings to runner, huge reaction. They also got hats with hidden compartments in the bottom and had a lot of fun/laughs pulling random stuff out of it. Another duo did an act but used items that were much too small and no one could see it. I'm sure they'll have fun.