Melbourne Victory head coach Kevin Muscat has praised his players for achieving a feat no other group has accomplished in the club's history.
The club is guaranteed at least two more games in the competition, at home on May 17 and away a week later against either Jeonbuk Hyundai Motors or Jiangsu Suning.
"It's a big achievement, considering we've had five attempts," Muscat said after the game.
"It's great for the football club. We've managed to create some history.
"We're through to the next round and I'm elated for the group.
"What that's given me now is an unbelievable thirst and hunger to go and win the next tie.
"We'll enjoy this one – we've got some time – but we'll immediately focus and turn our attention to our opponents for the next game."
The win over Gamba was Victory's first ever against the Japanese side, though it came with late drama.
With Victory needing a win to progress, it built a two-goal lead inside 20 minutes via strikes from Besart Berisha and Archie Thompson, until an 84th-minute goal from Gamba's Ademilson led to a tense finish.
"It was typical of our season tonight. We just left the door half open and gave them an opportunity," Muscat said.
"We would've liked to have got the third and killed the game off, but it's not in our DNA at the moment."
In the end, it was departing club great Thompson who netted the winner when he converted a pinpoint cross from Kosta Barbarouses.
The goal was his first of the 2016 ACL campaign and came eight years after Victory's maiden appearance in Asia's premier club competition in 2008, when he scored against Thai side Chonburi FC.
"We all had a sense that he was going to play a part at some point, in some moment that was going to give us more memories," Muscat said.
"In the end I think he was quite happy they got the equaliser because he'll go down as scoring the winner.
"It was written in the stars that he was going to come up with a moment. Just hopefully he's got one or two more."
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