"I was a Wishing Tree kid myself," he said. "My family went through a rough patch after Dad left. We were left with no Christmas basically, and if not for the generosity of Hamilton... my family wouldn't have had a Christmas at all."
Miller said Christmas was special for children and not getting presents can be upsetting.
"Its a sense of joy, just opening that present, wondering 'I know Mum couldn't afford this but this is amazing', like 'how did she do it?'
"Back then you're not aware of where it came from but you are just, like, my family cares about me."
As an adult, being a part of the Wishing Tree is how he could give back to others.
From sports gear to stationery - the gifts did not have to be purchased from a Kmart store and the more practical, the better.
"We're not about celebrating consumerism or making Christmas about what you get," Collings said.
"For us, it's about giving the gift of hope. About having children not feeling left out and giving gifts that are useful."
"For a child to have a nice backpack that doesn't make them feel left out when they are at school is really lovely for them to open, on Christmas morning."
Miller said gifts for the elderly were also needed because the older generation were often left out.
More than half a million gifts have been given out across the country since the appeal began in 1993.
This year, some Salvation Army Centres have a "Christmas loft" where parents in need can go and choose specific gifts to suit their children.
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