Greenwood is on the cusp of being ready, Cavani's still got it for another season after getting back to fitness, and I'm willing to give Martial one last season to prove himself. Ole plays with a single central striker and Kane, while world class, is surplus to requirements.
The single most important area for us to bolster is the DM position, because not only would it help settle our defense but it would unleash Fred or McTominay or Pogba to do what they do best. Pogba of course is capable of playing in the left upper midfield as well, but Fred and McTominay are both only capable of outstanding performances as box to box midfielders which they would be free to do with a reliable defensive partner in the double pivot. This is the single greatest return on investment available to us to bolster our build up play. I don't know if James Garner is ready to take on this responsibility week in week out.
After that, Sancho and a CB who's fast, good on the ball and willing to take the initiative.