I'm one of those who got a new Iphone for my self as a present when I got a new job. The thing is that i'm a fan of spotify and not of Itunes so I don't pay for my mp3 songs. The issue here is that you can't take a song from your itunes library and make it the ringtone. You need to buy that song from Itunes.

I found a webbsite called audiko.net where you can make your own songs or download songs already made by other users.

Download the songs form audiko.net and then open them in Itunes. Sync with your Iphone and voilá!