Klopp's Next Key Signing for Liverpool after Wijnaldum

So far, Liverpool have adequately reinforced their squad this summer by hiring key players under the management of Jurgen Klopp. Wijanldum became Klopp’s latest signing after sealing a move from Newcastle United.
However, the Reds still need to reinforce two key areas i.e. the strike-force and the left back position. The question is, who should be Klopp’s next signing after Wijnaldum?
The Merseysiders have an overcrowded strike-force at the moment with players like Sturridge, Origi, Ings, Benteke and Balotelli around.
Mario and Christian should be sold this summer and if they do leave Anfield, the Reds may look to sign a new striker.
However, they really do not need to sign a center forward because Roberto Firmino and Sadio Mane can also be utilized up front.
The German manager lacks depth in the left fullback position. Alberto Moreno was his first choice left back last season. The Spaniard was effective going forward but he was inconsistent at the back and could not perform the defensive duties well.
In such a scenario, Liverpool must splash the cash and sign a new left back to increase the quality and depth of the squad. The likes of Ben Chilwell and Jonas Hector have been in the limelight.
In your opinion, Who should Liverpool sign next?