There is a difference between betting and assigning a prize in a competition. Having contestants compete to win a prize in a competition is not a sin but betting on who is going to win is like gambling and is a sin. In dealing with each other the Holy Bible says, "Be kindly affectionate to one another with brotherly love, in honor giving preference to one another" (Rom 12:10).
"Let nothing be done through selfish ambition or conceit, but in lowliness of mind let each esteem others better than himself. Let each of you look out not only for his own interests, but also for the interests of others" (Phil 2:3-4).