Assuming United can spend 200M in the summer (which is needed for the finishing touches to the squad).
United need a CM, GK, RB and Striker.
I'd personally do the following:
Extend:
Diogo Dalot - 3 Year Contract (Promising and should fight for the RB slot)
Marcus Rashford - 4 Years with an option to extend to keep PSG away I think he will have a good run of form under ETH.
Garnacho - 3 Year deal
Alvaro Fernandez - 3 Year Deal (Squad option at LB)
Players Out:
Fred - £15-20m (30 years old when the season ends)
Dean Henderson - £20m (put nails his own coffin)
Donny Van De Beek - £20m (not what United need at this point although he was promising at Ajax)
Aaron Wan-Bissaka - £25m (Hasn't grown enough on the attacking front)
Luke Shaw - £30m (Trigger the extra year and let him go at this stage, he's hot/cold)
Eric Bailly - £6m (conservative) different fees touted but he will go IMO, will be great for Marseille
Alex Telles - £7m (not working out but still a good age and can be good in a Spanish or French side)
Axel Tuanzebe - £2-5m (anyone that takes him)
Brandon Williams - £5-8m (anyone that takes him)
Phil Jones - Free
Ronaldo - Free
David de Gea - Free
Total Outs (lower bound) - ~£125m
Players In - Assuming plenty of outs arranged early on to get the spent around £250m but much less due to the outs at the club:
January
Youri Tielemans - £15-20m (January, his contract expires in the summer and he's still a very talented player) I think he can play the deeper role and fight for the spot with Eriksen.
It also allows Eriksen to rotate with Bruno for the CAM slot when Tielemans starts in the DLP role.
Summer
GK - £65m
Not really sure the going rate on Goalkeepers or options, but getting DDG off the books for £375k a week saves United £19m a year, signing a goalkeeper on a third of those wages helps the budget for a GK, getting a top class young goalkeeper that has great distribution and stop stopping is essential.
At this point I'm not really sure "who" would be a good GK option, or if offering DDG much lower wages and extended for 3 years could be an option.
Striker - £75m
=1) Christopher Nkunku - £75m - Better all round goalscoring record than the others and in a stronger league, the others are risks and I'm not sure if United should sign a proven player or a gamble, United need quality to convert chances and I think barring a break out season from Leao or Osimhen that Nkunku is the best candidate.
=1) Victor Osimhen - £60M
2) Rafael Leão - £60M
3) Beniamin Sesko (assuming he can move) - £50M
Outside of Haaland who is just one of the best players of this generation, having a striker that can convert chances is a must. Nkunku is shorter than the other candidates but he is much better in front of goal. Equally first for me is Osimhen, he's also, faster and taller than Nkunku which obviously would have its advantages as a striker, Leao would be second.
CM - £110M
1) Jude Bellingham £110M - Generational talent, if Youri Tielemans joins it means that United are stacked for midfielders in the deeper role.
2) Frenkie De Jong £75M - If Jude is an option and he says yes, FDJ doesn't need to be pursued. if the squad still lacks depth in the area the DLP role outside of Eriksen and if Tielemans/Jude isn't an option then sign FDJ.
One of the two needs to be secured to make United have one of the strongest midfields in the league
RB - £50m Cap*
Not really aware of any top talents out there currently, Gusto is a player that is mentioned here but I know little about him
Total Spend (IF united extend DDG for much lower wages) £220m (or 120-160M with outgoings)
Total Spend - £300m (£180-220m with outgoings, this also ignores staggered payments or "add-ons" which might lower the bill more)