I think Gordon can move up a level from where he is, he certainly jumped levels from how he was at Everton to Newcastle. As it stands he needs more end product to jump to the next level, I think he can.
Its a similar situation to Madueke although I think Gordon has more to his game than Madueke and is more of a threat. We have seen more from in form Trossard and Martinelli but lets be honest, neither have played that well this season. Trossard still has better numbers than both Martinelli and Gordon this season but he has been frustrating.
Im not against the Gordon signing, Gordon is far less head down than Martinelli and far less prone to run the ball out of play when he goes down the line, Im not totally convinced it would be a good purchase though.