The selection of a DB will depend on Youboty. If he looks like a player, they'll likely take another position with the 1st pick, but I wouldn't be surprised if they still used a 3rd rounder on one.
Personally I think that the O-line should be addressed in FA, because I see the Bills moving Peters to LT and Gandy leaving for starting LT money next year. Ideally Butler will fill the hole at RT, but that remains to be seen. And if Preston can't become the starting RG, they'll need an upgrade there. Fowler and Reyes might be worth keeping, but since they're not all-pros, you could stand to upgrade there as well. But that's more fantasy than reality.
The Bills will have a big decision WRT LF-B, i.e. whether to give him the final, big money deal, or let him walk. I don't think DiGiorgio will be the heir-apparent, so this could be the position taken in the 1st round next year.
As for Kelsay, he'll be an UFA next year. He should be offered a similar deal to Denney.
And while the run-stopping of the D-line might be a concern, I'd like to see what a year in the Bills' strength and conditioning program does for guys like Tripplett and especially the rookies McCargo and Williams.