Realistic:
CB: Laporte b/o or Stones for crazy money
CM: Gundogan €40m?
Forward/winger: Griezzman b/o - he's a united fan iirc but also loyal to Atletico, who faced with a transfer ban....not sure, but it's doable or Sane (again decent amount of money will need to be offered)
Depth: Mahrez who'd add some quality as well
Free:
Abramovich could be a stop gap in the absence of real quality CF's in the market otherwise throw a shit load at Everton for Lukaku
Wild cards: surely Madrid will revamp their squad - so one of Kroos/Isco/James/Bale/Benzema might be surplus to requirements - not sure who Zidane likes/dislikes tbh. Maybe
@Vato @carvajal could add their opinions
And then, not sure how realistic but throw money at Reus or Aubamayeng or Dybala. Doubt anyone will be available
Laporte, Griezzman, Lukaku, Gundogan & Mahrez seem achievable. The rest have their doubts for various reasons