Sorry to say it..... Although tuning/ messing around with cars is fun. Unless you get a car with a turbo, your not going to get much for your money. If you go do the cams route, be prepared! I've had them in previous cars, they drink fuel (which didn't bother me), don't like the cold, or starting.
And from what people say on here, the standard air box with panel filter, is much more effective than an induction kit. I'm moving to a R27, as I had a fiesta st, which was n/a with cams exhaust etc, and it was a pain to live with. Bloody quick, but not worth the hassle.
If I was you, I'd get a cat back (for sound) as it won't give much more than 1bhp, panel filter, and decat/sports cat. Renault seem to have this little beaut set up fairly well.
Hope this helps.