I would NEVER give up Best for Ocho, Best is worth more. Dont be surprised if he is not your second best back come seasons end. As of now I would rank your backs
1.Turner
2.Mathews
3.Best(not far behind Mathews)
4.SJax
5.LT
I think you could get a better WR. Maybe offer Mathews since people are higher on him and go after like Roddy or Colston or Fitz or Marshall. Best and Turner would do just fine for you at RB.