I'm going to make the assumption that Bills will climb up into the top 7 or 8 spots in the draft and thus surrender their second first round pick. So we're operating on them having only 1 first rounder. But that first rounder will be--due to overall draft weirdness and unpredictability--Josh Allen! I don't know why I feel strongly that Allen ends up in Buffalo rather than Cleveland, but I just do.
As for Round 2, let's say the Bills end up having 2 second rounders after their trade. If Will Hernandez is available where they pick first in Round 2, the Bills should snatch him, but I see Hernandez being gone in the late first round. I do think the Bills will take someone like Isaiah Wynn, a versatile o-lineman, as soon as they're on the board after they get their QB.
For their second second round pick, I think the Bills will have to grab a WR. While Kelvin Benjamin provides a legitimate No. 1 in the prime of his career, Zay Jones is a concern and I can see the Bills addressing that need. I can actually see the Bills grabbing Michael Gallup out of Colorado State with their later second round pick.
Round 3, I think, is destined to be a RB. Every backup Lesean McCoy has gets taken by the Patriots (seriously, how many former Bills are on the Patriots?). I think the Bills will grab Kalen Ballage in the 3rd Round to play Brandon Jacobs bulldozer to McCoy's shifty/speedy run style. I think Ballage will be a great addition for Buffalo and will be a solid North-South runner for the next Ice Bowl that happens there. I think that Ballage's power and size can also help mask issues in the blocking up front, as that offensive line, after losing 3 starters, will need some time to find its rhythm.