The 1-1 draw at Manchester City on Tuesday night meant the Scottish campions finished with three points, their place at the bottom of Group C already confirmed before they travelled to the Etihad stadium.
Armstrong noted the improvement from the 7-0 defeat by Barcelona in the Nou Camp on match day one - they also drew 3-3 at home with City and 1-1 away to Borussia Monchengladbach - to the well-deserved draw in Manchester, albeit against an under-strength English side.
The former Dundee United player is already looking forward to next season’s European opportunities after the Ladbrokes Premiership leaders reached the group stage for the first time in three years.
“It was obviously a dream come true to play Champions League football but once you accomplish that, you want to do well in it,” said the 24-year-old.
“We definitely improved and it was an enjoyable occasion last night. Although there wasn’t too much up for grabs, a good performance by the team was important.
“We played well in large portions of the game, we kept the ball well, created a lot of opportunities, maybe we could have had a couple more goals and taken all three points.
“But we have been improving the whole time since the campaign began and we are happy with what we produced.
“It is not about proving a point, it is about learning and developing and I think we did that from when we started the campaign to where we are now.
“It gives you a hunger to come back next season again and keep improving and keep on being there.”
Craig Gordon has enjoyed Brendan Rodgers’ first attempt with the Scottish champions since taking over as boss in the summer.
The Celtic goalkeeper, looking ahead to the trip to Partick Thistle on Friday night, said:
“We want to try to get back there [to the Champions League]. There is a lot of hard work between now and then to make sure that happens so we get back to working in Scotland and give ourselves the opportunity to try it again next year.
“Since the manager has come in, he has changed a few things and put in place patterns of play to make us better and the confidence to go out and play and make sure we get results.
“The last two away performances have been good draws and hopefully we can take that forward and try to give it an even better go next year, if possible.
“It is on to the next game. We want to continue to play the way we are playing, it is enjoyable to play in.
“We are playing some really good stuff, creating some good chances so if we continue doing that then everyone will be happy.”