We have two things to sort out - quality and squad depth. I would pay up for Sancho to resolve quality in the front line. Rashford, Martial, Greenwood and Sancho would give us nearly 10 years of top quality options. But if Dortmund are being ridiculous and wanting 108 straight up cash and not even split payments or whatever the reason for the transfer failing then Id sort out the squad depth and then look to spend big next year. I dont think Covid will be sorted any time soon, so if Dortmund think they will get more money next year they are in for a shock.
To sort out squad depth Id take -
Zaha 45 (at this price due to 25 percent sell clause) - Yeah everyone will poo poo this idea after Sancho. But he is a proven prem player that can cover RW and LW and he suits Oles style to T. Fast, Tricky, Direct. Will get 10 goals/5 assists at least.
Badiashile 30 - A bit young but Left Footed CB, Fast and looks a good player. With all the crocks at least (hopefully) he will provide backup.
Reguilon 30 - La Liga LB of the season. Young. Can attack. Won Europa. Cheap. With Shaws injuries its a no brainer
That would sort out all the main back up areas except striker and defensive midfield but we have decent if not ideal options to cover for Martial ( Ighalo, Greenwood) and Matic (Fred, McTominay) if need be.. Next year we will have solved the squad depth after the above signings and can blow money on quality - Sancho, Haaaland, Upamecano whoever