Real Madrid already has the best players in it even though they are reserve players, Carlo Ancelotti does this so that he has lots of choices because if there is an injury storm like last season he doesn't need to worry because he is very good at rotating players.
The squad currently owned by Madrid is indeed quite capable, both main and reserve players, but I think that in order to maintain their chances of retaining the La Liga and Champions League trophies next season, Madrid must still be able to bring in several new players, especially their defense line, because this season Madrid often have to fight hard to maintain their victory in several matches, so far Ancelotti has often rotated player positions when their defense has had problems, such as this season where several midfielders have become defenders, like as Lucas Vazquez and Aurelien Tchouameni have done.
I think that even though Real Madrid recruited a lot of players, they didn't spend much on their budget because they got Mbappe for free, at least 150 million euros he could spend on other players who certainly have good potential.
Several Madrid players have the ability to play in different positions, but Ancelotti cannot continue to do this considering the busy schedule next season, so regardless of how much money Madrid have to spend next season, buying defenders should be their main focus at this time, by having several reserve defenders, so at least Ancelotti no longer needs to shift the positions of several players in important matches later.