I'd advocate signing a new player. This kid has shades of Verratti, Gundogan and Santi.
He can pass it anyway you'd like it, can collect and bring the ball out from deep with pace, dribble in tight areas and always seems to find space. One thing that I really like about him is that unlike many of our midfielders he instinctively knows when to release the ball, he doesn't dwell on it and has an exceptional football IQ for his age so seems to make the right decision more often than not.
In addition to his passing and dictating ability he also has a huge appetite for closing down and realishes the defensive aspect of the game, has a huge engine so can run all day long. Easy to see why he's one of the next big things in Germany, currently has less than two years left on his deal and so likely wouldn't cost anymore than £25mil plus he used to have a pretty good partnership with Xhaka. Would be exceptional value and is being linked to Liverpool of all teams, it just takes too much sense to sign him.
Our midfield needs to be culled with players like Ramsey given the boot but under Wenger it'll never happen, he's holding the team back in so many ways at this point.