At 16, I agree with buying a used, 'slower' car. Like mentioned, used WRX, modded Civic, or hell even a 240sx with a stock swapped SR motor will be fast enough. I recommend the 240 because:
1 - it was my first car...at the age of 23. So I'm a bit biased.
2 - it's RWD, so you can get a feel for how they drive
3 - cheap buy/maintain. SR swapped 240s go for 6-7k on average. less if you're looking for a stock KA motor or the older body style.
4- It's a good platform to learn about cars. Everything is basic. No crazy electronics/gadgets
5 - still in the Nissan family
If you're insistent on getting a Z. Good luck, and
if/when you do.