I think it highly unlikely the Bills will trade--not because they don't want to, but because the asking price will be too much. Other teams are thinking the same thing, and it will become a bidding war of magnificent proportions.
I don't see Beane selling the farm to get any of the top four, and for this reason, I believe that either Rudolph or Jackson will be there at 12, and whichever one is, will be your Buffalo Bills first pick in the 2018 draft.
That is probably too high for both, but if you want to draft a starting QB, they will be your best options at 12. Personally, if both were there, I am most intrigued by Mason Rudolph, but I would not be disappointed with either at 12.