I think PSG squad is already very solid to compete in this year Champions League so there is no need for them to bring in other expensive quality players into the team because it could damage what has been established so far, but if they want to add players Luis Enrique should focus on a solid reserve goalkeeper or defensive midfielder just to rotate the core players so that the balance is maintained.
Enrique has shown that he can prepare young players and they will match the high level of the team, so do not underestimate the players that are currently in the team. The current roster and bench were enough to win all the tournaments they participated in last season, if this is not enough now, I am sure that they will be able to afford to strengthen any position, they have enough money. But Enrique has already shown that he is not a supporter of large transfers, and acts only when necessary.