Van Gaal has added the likes of Radamel Falcao, Angel Di Maria and Marcos Rojo to his squad following a slow start to the season, which has seen United pick up just two points from three Premier League matches and exit the League Cup at the hands of third-tier MK Dons.
Asked by The Guardian whether he thought Van Gaal could be a success at Old Trafford, Cruyff - who once tried to block the 63-year-old's appointment at Ajax - said: "We hope so because it would be good for Dutch football and other Dutch managers.
"But how it will go? You never know. It will take time."
However, he feels keeping all those star players happy could be crucial to the prosperity of Van Gaal's tenure.
"There should be a logic always but the big problem is to manage all these players," he said. "It's the same thing with Barcelona.
"They now have [Luis] Suarez, [Lionel] Messi, Neymar – how do you play them together?
"If you see them individually then, of course, they are great players.
"It's the same at Manchester United. Individually they are great but they have to play like a team.
"So then you get another problem. They are all famous. They earn a lot of money both on and off the field. How can you create a team and bring all these egos together?
"The main goal for Manchester United is for them to play well – and not have a player saying, 'I play well, I scored two goals'. Because if I score two goals but three goals go into our net then we lose.
"They provide [Van Gaal] with a lot of good players but he has to turn them into a team. And you can't arrange the chemistry of the team in two weeks. It needs time.
"It could be possible that things work. But, once again, can these people develop their own game for the sake of the team? It’s not easy."
Manchester United host QPR in the Premier League on Sunday.
