Again, you can't judge based on words like "best" and "worst." The champs are largely all balanced as far as how "good" they are in an absolute sense. You have to find one that works for you. I main Ziggs, and I will agree with what OneSixthIrish said: if you like Fiora, then you'll prefer Ahri to the little badger. Their play styles are oddly similar...
Find out your play style of choice and then buy a champ who matches it.
Also, don't worry so much about how many 6300ip champs other people have. Jax is one of my absolute favorite champs, as are Teemo, Katarina, Irelia, and Akali, and they are all priced well below 6300. In fact, I play them and some other cheaper champs more often than any expensive champ...