Assuming the top 3 RBs are gone, you start with Antonio Brown and go from there. If the top 10 RBs are gone by your 2nd round pick, go WR again....like Cooper or Dez. The usual RBs available at 2.9 are Gurley and Fournette. I would rather punt at RB and take another WR and hope Gurley or Fournette is there in round 3.
Just let the draft come to you. That said, there is a good chance Brown goes in the top 3, so you could get Elliott at 4 (assuming he's not suspended).
But there's nothing wrong with starting a 12 team PPR draft with Brown, Dez, and Watkins, which is very plausible drafting from the 4 hole.