I chose infielder...but now that I had a chance to think about it, a top of the rotation starting pitcher (through FA) is what this team needs the most to win in the playoffs.
My original view was I just wanted the team to make the playoffs and shoring up the infield is where I think the most improvement could come from. Now that I think the team has a decent chance to make the playoffs in its current state, winning in the playoffs is the next step. And I agree the Jays need an "ace" who can pitch in the big game especially if it comes down to a one game playoff.
The caveat to this is I don't want the Jays to trade for an ace. They would have to give up too much for my liking. I like the team's chances in 2015 and 2016 with this roster. I'll like the team's chances slightly more in 2015 and a lot less in 2016 if a trade for an ace results in one of Hutchison and Stroman and one or two of Norris, Sanchez or Osuna as a starting point going the other way.