Just so you know, Comixology's got a huge sale on Amazing Spider-Man today, $0.99 per issue. I highly recommend, if you have the money, getting #611-#637. But if you have to get picky with them then the three Electro issues, the two Rhino issues (spaced pretty far apart), the Lizard ones, and the Grim Hunt ones are the way to go.
Marvel Monday Sale Digital Comic Collection - comiXology