I wouldn't advise buying anything to reach 16. Neither 15 nor 16 are likely to be a final margin of victory, you'd just be risking extra juice with very little chance of it making a difference.
For the record, I like Ball chances to win by at least 20 tonight. They just turned down an invitation to play Boise in the Humanitarian Bowl (understandably so, as that would be like voluntarily playing an extra road game), so this is their big chance in the spotlight. They don't feel confident they could beat Boise, but they'll try and make an impression by piling on the points tonight, I expect. I think this and I've loved betting Buffalo as a dog all season.