At BEST?
City
A new GK. Donnarumma? Or they could just get a safe option like Valdes.
They will need new fullbacks with the departures of Zabaleta, Sagna and Clichy. And the likely options seem to be Walker, Rose, Gaya and Fabinho. Any two of those four and they will have strengthened.
They will probably get a new winger to make up for losing Navas and potentially Nolito so I think it's likely they might buy someone like Muniain or Castolo.
Liverpool
I don't see them attracting any major names but I could see them signing Timo Werner and Oxlade Chamberlain. Naby Keita would probably be the best coup of the lot if they can manage to get him. Imagine him and Mane linking up. Also could see them signing an English keeper like Pickford, Hart, Butland or Forster. I don't believe Casillas will join them.
Chelsea
They don't have to strengthen many positions but Bakayoko would be a big get for them. And if Costa leaves, they're definitely gonna buy a striker and that could be Lukaku unfortunately for us.
Spurs
I can't see them making many big signings to be honest. I think they might lose Walker or Rose as well. And potentially Dier. If that's the case, they might buy Luke Shaw to replace Rose.
Arsenal
Lol they won't sign anyone. They'll probably lose both Sanchez and Ozil to Bayern.