A4 Vs. Gti... Help

hey i drive a 1999 audi a4 2.8l. i am looking to make my car faster than my friends gti. i am kind of new to this so i am not sure what i can do, any help? is it worth it to add a turbocharger, or to supercharge it? what lse can i do to make my car faster?

thanks,
jin

Supercharger as it will be a lot cheaper