Now the Rangers kid is determined to pick up where he left off as he looks to make the transition from Murray Park prospect to Ibrox star next season.
As Ally McCoist's side cruised over the League One finishing line in the final few weeks of the campaign, Gallagher was one of the few talking points for the Light Blue legions.
After marking his Gers bow with a goal in the 2-0 win over Dunfermline in March, he would play a key role in the Scottish Cup victory over Albion Rovers a few days later and show up well in the wins over Brechin, Arbroath and Ayr United as the champions went unbeaten in the third tier.
It may have taken until the final few weeks of the campaign for Gallagher to make his breakthrough but the 19-year-old showed that he need not be a one-season wonder as thoughts turn to the Championship kick-off.
His final game of the term came last week as he helped Gordon Durie's side to the SFA Youth Cup, the Light Blues lifting the silverware in dramatic fashion after a penalty shoot-out success over Hearts.
It was the perfect way to round off Gallagher's breakthrough season, but the forward admits the final whistle of the campaign came at just the wrong time for him as he settled into life in the Ibrox spotlight.
"I think the season did end at a bad time for me," he said.
"I was getting more accustomed to being with the first team and being in the first team fold and with the players and in that environment.
"The scale of everything at first-team level does take a while to get used to, in terms of the crowds, the pressure, the expectation, and I was getting more used to it.
"So, in a selfish way, the end of the season did come too soon for me.
"But all I can do is focus on working hard over the summer, making sure I come back sharp, and hopefully I can pick up where I left off."
With his boots now packed away, Gallagher can enjoy his summer break and reflect on a job well done after he made his move into McCoist's squad and played his part in successes for the Ibrox first and second strings.
While the close season will give the Gers stars some well deserved down time, the hard work is continuing for McCoist as he looks to shape his squad for a shot at Championship glory.
Rangers are now just one title win away from a return to Scotland's top tier, but after two seasons of slugging it out against part-time opposition, they will face a far sterner test next time out.
Even if no new players arrive at Ibrox in the coming weeks, McCoist's side should still have enough quality to see off their Championship rivals and claim the silverware.
Gallagher is determined to be in the best shape possible to ensure he can mix it with the likes of Hearts, Falkirk, and maybe even Hibernian next season.
He said: "I have always had a good focus through the summer. We get programmes given us to do over the summer and I will do that.
"But it is important that you have a bit of down time at the start. I will maybe take a shorter break this time than I would had I not been involved with the first team. I will come back as fit as I can be."
After months of physical exertion, the lengthy summer break will give the Rangers stars a chance to recharge their batteries and recover from a campaign that saw them only drop six points in League One, reach the Scottish Cup semi-finals and the final of the Ramsdens Cup.
Midfielder Nicky Law admitted last month that he couldn't wait to jet off on holiday to get a temporary reprieve from the mental pressure of being a Rangers player after his first campaign in Light Blue saw him, and his team-mates, analysed and criticised like never before.
It is a situation Gallagher will, if he can maintain his place in McCoist's squad, have to handle more next season and the youngster knows the expectation from the stands will never lessen at Ibrox.
"It doesn't matter what level you are playing at, there is always a level of expectation and pressure at Rangers," he said.
"The boys certainly did themselves justice. They went through the season unbeaten.
"There have maybe been a few lapses in performances, but you can't ask for too much better in terms of the results.
"I have had no real experience of the criticism, everyone has been nothing but nice to me, which is great. That might come next season!"
It is not just on the field where Gallagher has been thrust into the spotlight in recent weeks, with his commitments away from the training field or Ibrox on a matchday steadily increasing as he has become a more familiar face in Light Blue.
From press conferences and photocalls to promotional events and school visits, the Gers kid has handled life in the media glare with a maturity beyond his years and is relishing everything that comes with being a first-team star at the club.
Gallagher said: "It is strange. I am asked to do a lot more away from football and it is unreal how quickly things change for you when you are pushed into the spotlight.
"I do love it, though. It is something that comes with playing for Rangers. We have got a great foundation at Murray Park, we are all well prepared and informed and know what to expect.
"It is not an issue being able to handle the exposure you get of being a first-team player."