The striker scored the only goal of the game in Palermo on Friday as Cesare Prandelli's side moved seven points clear at the top of Group B of the European qualification section with just three games to play.
Gilardino struck seven minutes before half-time as he met a left-wing cross from Antonio Candreva to head home his 19th international goal from close range.
The three points means they will qualify for Brazil if they match Bulgaria's result with Malta when they host Czech Republic in Turin on Tuesday.
And the 31-year-old hopes to be celebrating after Friday's win set them up perfectly to secure their passage to next year's showpiece in South America.
"I'm happy to have managed to get the breakthrough because it has been a very complicated match," he said. "Their defence (Bulgaria) was extremely tight and it has been difficult for us to find spaces.
"Therefore I'm very happy to have managed to unlock the match thanks to my goal.
"On Tuesday we'll be playing against the Czech Republic in Turin and we want to close this phase in the best possible way.
"We want to make a good performance in order to win and celebrate the qualification."
Defender Giorgio Chiellini echoed his team-mate's comments and admitted he was proud of their performance against Bulgaria.
"We usually suffer during the first match in September," he said. "It has always been so in the past.
"We had a good performance in the second part of the first half of the match by holding the ball's possession and trying to find spaces.
"In the second half of the match we have been a bit too static, probably due to our physical condition.
"In any case we're happy for the result which brings us closer to the qualification. We hope we'll be able to celebrate the qualification already in Turin next Tuesday."
