Pogba and Rashford - really need to have options to replace these two because they frankly have far too many off days where they appear to just be off the pace/lazy/out of ideas.
But the single most important thing for me is to buy two attacking fullbacks (or give Dalot a chance). Without that option, it is far to easy to defend against us. If you cant get fullbacks overlapping your wingers, your wingers become ineffective. This was as true with fecking Irwin/Giggs and Neville/Beckham as it is today, but we seem to be blind to the obvious problem, and we have been for years.