Wales now face Lions conquerors South Africa on June 5 in Cardiff before Kiwi Gatland returns to his native homeland for a two-Test tour.
And despite finishing fourth in the championship, Ospreys utility back Hook believes Wales can compete against the very best in the world.
"The win will give us great confidence going into the summer tour in New Zealand," said Hook, who was a pre-tour call up to the Lions squad having missed out on original selection.
"We know we have a lot to work on but we have beaten quality opposition and can build on this.
"It is nice to have South Africa first up and we hope to get a result here before a massive tour to New Zealand.
"We have had a disappointing Six Nations campaign but the games in the summer are all massive. We want to give the players, coaches and supporters what they deserve. We are looking forward to it."
Prior to the clash in Cardiff, Gatland admitted jobs were on the line for himself and his coaching staff following a below-par campaign as Wales set out to avoid collecting the dreaded wooden spoon.
But Hook insists the under-pressure Wales squad will stick together as they prepare for the 2011 World Cup.
"We want to do well for the coaches and the team in every game and today was no different. But, to be honest, we do not think about things like that," added Hook after the game.
Gatland himself was quick to praise Hook's contribution at the weekend, with the Lions' forwards coach more than happy with the way in which one of his big-name players is developing in a new role.
Having played fly-half, inside centre and full back for his country, Hook was switched to outside centre for this year's Six Nations and Gatland believes the move could pay dividends for years to come.
"James was very good," said Gatland.
"He is still learning when to make certain decisions at that position but he took his tries very well. He looked very dangerous.
"He's such a talented player. You don't want a player of that ability and talent not being on the park. At the moment our centre combination is working well and it's creating a lot of opportunities."