A lot of the characters of Naruto serve one purpose or another. Luckily for Kiba, as a part of the Rookie 9, he has more of a better role than his character gives credit. You can tell that he isn't one of Masashi Kishimoto's favorite characters, since he doesn't appear much in Kishimoto's artbook; the one picture that has him doesn't even show his face!
Kiba serves almost like a puppet to show off Naruto's growth during the Chuunin Exam. At the end of their battle, Naruto states: I've.. become stronger, and after that, Kiba becomes friendly to Naruto also. This also proves that Naruto has a specialty that, everyone he meets, he makes friends with him (or most, anyway, as Kakashi speculates).
Another major role Kiba plays is to track; when Uchiha Sasuke sets off to go join the Sound, Kiba helps track where exactly he was, and was to battle Ukon and Sakon of the Sound Five. He wasn't able to defeat the two brothers, and so Kankurou came to his rescue.