Having formally started his Old Trafford tenure on Wednesday, Van Gaal took his first news conference as manager of the 20-time English champions on Thursday.
Boasting coaching experience with the likes of Barcelona, Bayern Munich and, most recently, Netherlands, Van Gaal has clinched league titles in every country he has worked in.
The 62-year-old is now tasked with returning United to the upper reaches of the Premier League after they finished seventh in David Moyes' first term in charge.
However, Van Gaal would not be pressed on a prediction or a target for his first season at the club - instead calling for patience in assessing his squad.
"I do my utmost best. I cannot give predictions because you never know. It's the biggest club in the world," he said.
"I have to prepare a team and adapt to this big club. It shall not be easy but when you see my career you see what I have won and that I can say.
"The future shall show if I can do that again. This is the biggest club because of being known worldwide, but you are never the biggest club because every season, you have to prove and last season you are seventh.
"Then you are not the biggest club. I worked for Barcelona, in my opinion the number one in Spain, at Ajax we were number in the Netherlands and at Bayern, number one in Germany.
"Now I am in Manchester - the number one in England. I hope I shall fulfil expectation. It will be difficult."
Van Gaal led Netherlands to the semi-finals of the FIFA World Cup in Brazil and takes over from Moyes - sacked in April after a dismal tenure at Old Trafford.
Under the Scot, United missed out on European qualification for the coming season, with Van Gaal's reign likely to be a much stricter regime.
United have already brought in Luke Shaw and Ander Herrera from Southampton and Athletic Bilbao respectively, but Van Gaal said the club's current crop will have chance to stake their claim for a place.
"My motto is always the same. I want to look at the player now, the players present. I know the players but I don't know the players I have coached," he added.
"I want to see in the next first three, four weeks. Then maybe I shall buy other players. Shaw and Herrera were already on the list so I gave my approval because I like them.
"First I want to see the players performing my philosophy. I have to see how the players perform my philosophy. Then I can answer [what would be a success].
"I have not worked with most of them. It is very important there is a click between [them and me].
"For me, the challenge is [to finish] first but you have to analyse after one season - it is dependable on the click between manager and coach."
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