The PSV attacker has already cost United over £20m but reports suggest Louis van Gaal could surpass last year’s total of £150m, with the likes of Mats Hummels and Nathaniel Clyne also strongly linked.
With Van Gaal all but confirming a midfielder is on his list, plus the possibility of a new striker, United are in a good position to strengthen ahead of a return to the Champions League final.
“What they have to do next season is challenge and get closer to the title,” said Neville.
“They’ve already started buying the players. Depay has come in already so it looks like they’re going to be aggressive and on the front foot in the transfer market again.
“It needs that really. If you look at Manchester United’s squad at this moment in time it won’t get close to Chelsea, as it currently is.
“But with three or four signings, the right ones, then they can challenge Chelsea for the title next season. Arsenal and Manchester City will feel the same.”
With Van Gaal seemingly targeting a top class holding midfielder, rumours with circle over any potential targets, especially after it became painfully clear how much the missing Michael Carrick affects United’s play.
Neville added: “If Michael Carrick gets injured, he needs someone in holding midfield.
“I would think the right-back position is going to be looked at, either as support to Antonio Valencia or someone to take the number one spot.
“I think probably a wide area and it depends what he does with Robin van Persie and Radamel Falcao at the end of the summer. There will be a big decision in the forward area as well.
“There’s still probably three or four names to be added.”
Whatever happens, it’s certainly going to be another exciting summer for supporters, with another unprecedented spending spree on the cards.