I would prob try to do a swap deal Busquet (bad presence in the locker room, no proactivity in camp both in the defense side and offensive side) for Erikensen, get rid of Coutinho, Dembélé and Semedo, use the money to get Neymar and a good defender (don’t really know who, maybe I will do some research and add this later). On a side note, You could also try selling either Griezmann or Suarez and buy Lautaro, I think a 4 2 3 1, with Messi and Neymar playing wings, Griz playing as a second striker and Lautaro/Suarez as the central striker would be good. Passing midfielders with good defensive skill, like De Jong, Vidal, Eriksen (maybe they could buy additional players with this money, I would look out for the likes of Pavard for fullback and Brandt at the midfield if they really want to get younger). Something like this:
De Jong Eriksen
Rakitic, Vidal, Pjanic, Puig and Ansu Fati would be great off the bench to give a extra boost to this team.