Red Devils legend Neville thinks it's inevitable that Guardiola will leave City and Mohamed Salah will depart Anfield.
"Manchester United have to build block by block and wait a bit," said Neville on Sky Sports.
"They have to make sure they make the right decisions because every time you have a bad transfer window it takes two to unravel it and they have to stop doing that. This summer has been solid, if not spectacular, in the market.
"It's a case of can Manchester United get a couple more signings in January and then two or three next summer and slowly rebuild what they want here, which is a team of players who want to be at the club and are committed and motivated and have the quality to challenge for the title.
"It's never too far away. Pep Guardiola will leave Manchester City in the next few seasons, Jurgen Klopp might lose Mohamed Salah or another key player and then all of a sudden you have to be ready to step in and challenge if it's there to challenge for.
"Wan-Bissaka is young and has potential, and they needed Maguire, who is a personality and dominant force at the back.
"It's the start of something. They will have to be patient. They have a new strategy, it's probably the fourth in the last eight years, but stick with this one.
"Don't keep going down a path and then ending up back at the roundabout and going down another path and doing the same thing. You have to stick with a strategy. There has been a lack of that in the last few years.
"It ended up being a brilliant day for Manchester United. I don't think Ole will get too carried away. He will know it's early but he will think it's a big moment.