The midfielder scored the extra-time clincher as Blues overturned a 2-1 first-leg deficit to complete a 4-3 aggregate win in the Carling Cup semi-final and set up a final against Arsenal next month.
And he told Sky Sports 1: 'It's unbelievable, you dream of these things.
Birmingham 3 West Ham 1 (aet, agg 4-3): Gardner nets the big one and sends Blues through to Carling Cup final
City hero: Graig Gardner caps dramatic fightback for Birmingham
'I was saying to my mates I wanted to get the winner to take us there and to do it was unbelievable.'
Carlton Cole's screamer to open the scoring on the night had put the Hammers 3-1 ahead on aggregate before Lee Bowyer and Roger Johnson set up extra time.
Keeper Ben Foster admitted Birmingham had done things the hard way, saying: 'As always, it takes a goal against to get us going.
'(The final) will be a great event for the fans, it's been a while and for a lot of the lads, it may be the only time we play in a final.
'We've got nothing to lose, its a one-off game and anything can happen. We've just got to play like we did in the second half and hopefully get the result.'
Big deal: Birmingham players celebrate reaching Wembley final
Manager Alex McLeish added: 'We were down and out, I said to the players at half-time that to all intents and purposes we were out of the cup.
'I had to make the change and have a instant impact. I said to them if they get a chance to cross, to put it in the box for the presence of Zigic. It was his best game for us, he was very difficult to handle.
'We tried our best in the first half but we huffed and puffed without troubling them. Zigic made the difference. It will be an enormous pride for me to lead the team out at Wembley, it's a dream come true.'
Gardner was twice denied by the woodwork in the 90 minutes, and McLeish acknowledged: 'It was third time lucky, and it was a tremendous goal.'
Gardner himself joked: 'I just kept trying - as 'Fozzy' knows, when I let one go it's hard for the keeper!'
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Explore more:People: Carlton Cole, Craig Gardner, Roger Johnson, Lee Bowyer, Ben Foster, Alex McLeish Places: Birmingham