Gardner's 47th-minute strike settled a tight 1-0 Premier League victory over the Magpies at the Reebok Stadium on Sunday afternoon.
The Jamaica international's superb strike capped a fine day for Megson after the club had earlier confirmed the manager had agreed terms on a rolling contract.
Gardner has not been a regular in the Bolton starting line-up this season but scored within a minute of entering the fray at half-time to send a signal to his manager.
"I'm ready when the manager is ready for me," Gardner told Setanta Sports 1.
"I was hoping to come on and get the winner - it's a great result.
"I just went on and gave 110%, the lads were brilliant in the second half."
Team-mate Matt Taylor added: "It's massive, he had a bit of a point to prove with not being in the team."
The former Portsmouth midfielder added that the team are delighted with their current run of form.
"I think it takes the pressure off. We're looking upwards instead of downwards.
"We've got a game on Wednesday now against Stoke now and I feel like we're getting into good form.
"We've been playing decent stuff. That's three wins on the bounce at home so we're very pleased."
Megson was relieved that his side were able to hold on for the win despite coming under pressure from the Magpies in the closing stages.
"Whilst it was 1-0 and Newcastle were pressing as they were in the last 15-20 minutes it makes life very difficult for everybody," he said.
"It was to be expected, it was a huge game.
"When we got the ball we weren't keeping it well enough and we weren't causing them many problems after we scored really.
"But it's a great result for us."
Megson also played down the significance of the announcement regarding his contract earlier in the day.
"It's not a new contract," he revealed.
"When I signed it last week that was the first time I've signed a contract here, so it's not something that's a big deal at all to be honest."
Newcastle caretaker boss Chris Hughton, meanwhile, felt one or two moments of lost concentration had cost his side.
"I think on the balance of play we had the better opportunities but had some lax moments where we switched off," he said.
"We applied enough pressure to get back into the game.
"The important thing for us was the performance. To come here against a direct side, a very strong side and be able to contain them for the large majority of the game speaks volumes."