Goals from Robin van Persie and Luciano Narsingh earned the Dutch their first three points in Group D on the road to 2014.
But Van Gaal, who had included several new faces on his return for a second spell as coach, warned he expects a higher standard from many of his players.
Jordy Clasie and Daryl Janmaat were singled out for criticism, while only a significant improvement after half-time spared Bruno Martins Indi and Jetro Willems.
"Janmaat was not Janmaat," Van Gaal told De Telegraaf. "Clasie can offer a lot going forward, but he did not. That's why I changed them after the break."
Ricardo van Rhijn replaced Janmaat at half-time, with Clasie giving way to Leroy Fer five minutes into the second period.
Van Gaal added: "In the first half I was also dissatisfied with Martins Indi and Willems, but in the second half they improved handsomely.
"That is very impressive at that age and says a lot about those guys."
Despite his concerns, Van Gaal was pleased with a result which was a marked improvement on his last qualification campaign at the helm. The Oranje failed to qualify for the 2002 World Cup in Japan and South Korea after being held 2-2 at home by the Republic of Ireland in their opening game.
"Where then we started badly in the (Amsterdam) ArenA with 2-2 against Ireland, now we have a good start," said Van Gaal. "That's wonderful.
"It is very important that we have won the first game, otherwise you are immediately behind the pace.
"I think the public enjoyed it, you could see that from their reactions. We had many more chances than the Turks."