Newcomer Looking for Suggestions and Insight

Hey, I'm new to the forums. Up front I want to say that I'm a new driver and plan to delay the upgrades until I become more experienced.

I'm 16 and recently got a '03 v6 Mustang. I'm loving it, but I want to learn more about my car and look into some future upgrades. I've been looking around some forums, and I've come up with some ideas.

Right now I'm looking at purchasing either a CAI or a dual exhaust. From my understanding, a CAI would run me about $80 while a dual would run me $300-400. Honestly, being a teenager, I'm looking some something that would make me feel/look/sound cooler in my Mustang. From what little knowledge I have, the duals would benefit me most.

With this introduction, I have a few questions

Are there any other economical upgrades I can make to give me a bit more push, sound, or style?

What else accompanies the aforementioned upgrades? (installation, other costs, tuning, maybe even insurance or emission repercussions)

What other upgrades should I educate myself about?

Please go easy on me, I'm pretty ignorant. Any elementary explanations are welcomed, even appreciated, so long as you extrapolate. I'm sure I'll have more questions in the future.

Also, should I look into joining an autocross club, or signing up for advanced driving classes? Off topic, but input is appreciated.