We will get Verratti, in 2019! He will still be 26-27 then, which should give him at least 5 solid years with us. I'd go all out for James in the summer; I'd even sacrifice Berardi if it meant securing James.
We've already secured Caldara for the 2018 season, and he'll spend next season on loan at Atalanta. As for the midfield, Bentacur and Mandragora will most definitely spend next season on loan somewhere else. We need reinforcements in midfield, and Nzonzi (experience), Tolisso, and Dahoud seem like realistic targets (young, talented, lots of potential). I'd love for us to get that Mbappe kid from Monaco (they have so many interesting players), but we can't buy everyone. We need a competent RB/RWB as both Licht and Dani Alves are unreliable and ageing. Grimaldo and Danilo are options I guess.
In terms of youth prospects, we should try and secure both Orsolini and Pellegri, and make sure we secure the few unpolished gems we have in our youth setup.