IMO, we have 5 players in our team that will be definite starters next season. They are De Gea, Valencia, Bailly, Herrera and Pogba. The rest of the positions can be strengthened but we need to choose the ones that are most important. We can play two formations, 433 or 4231.
De Gea
Valencia----Bailly----CB------LB
Herrera
CM------Pogba
RW--------CF--------LW
De Gea
Valencia----Bailly----CB------LB
Herrera---Pogba
RW-----CAM/SS------LW
CF
CAM : If we sign Griezmann, he will either play the CAM position in a 4231 or RW position in a 433. I don't think Joe would play him as a CF. That will cost us around 85m pounds.
CF : We have Rashford and Martial. Going into a new season depending just on them would be madness. We definitely have to sign a striker. Morata, Lukaku, Belotti, Aubameyang, etc are some of the options. Lets say this will cost us a minimum of 50m.
CM : We have Herrera and Pogba as starters. Fellaini is a good option from the bench. So we have to get a CM/CDM depending on where Herrera will play long-term. We can try for Naingollan, Fabinho, Dier, Matic, Naby Keita or Paredes.
RW : If its a 433, Griezmann will play there. Else it's between Mkhi and Mata. I can't think of any player that we can add who would be a significant improvement over these two. So unless we sign a player like Bale or Sanchez, there is no need to buy anyone.
LW : We have Martial who has had a terrible second season. Mkhi can play here if the formation is 433. Lingard will be a bench option. Again can't think of any player who is clearly better that we could sign.
CB : Rojo is our best LCB. But it might take a while for him to recover from the injury. We also have Smalling, Jones and Blind who can play there. If we sign someone, we need to get rid of a few first.
LB : There are no clear frontrunners for this position. Darmian looks the best bet at the moment. Shaw and Blind can also play there. Both Blind and Darmian can't support much in attack. Shaw looks like the player we need but is yet to show it. So I think we'll need to sign a new LB. Mendy would be my choice.
So we have to sign a striker and a CM apart from Griezmann. These signings are a must. The other positions will depend on whether we can get a top player for that role. My preference would be to add a LB. The final line-up would be
De Gea
Valencia Bailly Rojo Mendy
Herrera
Naingollan Pogba
Griezmann Morata Mkhi
Subs: Romero, Smalling, Mata, Rashford, Martial, Fellaini, Blind