At Wide Receiver, I think that we can sign two players. Calvin Ridley would be a dream come true, but he will be tough to sign, so Darnell Mooney could be more realistic. Hollywood Brown would be good too.
After that add another player like DJ Chark, Donovon Peoples-Jones, or Van Jefferson.
This would help our WR group immensely.
At Safety, I'd love to get Darnell Savage, but would be fine with Jeremy Chin.
As for Running Back, just re-sign Ty Johnson.