Paolo di Canio's side suffered an embarrassing opening-day defeat to notoriously poor travellers Fulham, despite dominating for the most part at the Stadium of Light.
The roles reversed at Southampton, where Emanuele Giaccherini's early header looked set to decide a one-sided clash. Jose Fonte's goal two minutes from time eventually saw the points shared, but Gardner was pleased with the Black Cats' performance.
"We expected them to throw everything at us," the midfielder said. "They were at home for the first time in the season.
"We expected that and against Fulham we did absolutely everything apart from find the net.
"We came here and I thought we did really well. Yeah, they were on top but they never really broke us down.
"I thought we defended brilliantly as a team and the 2,000 Sunderland fans that came down were absolutely unbelievable as well, singing their hearts out.
"Hopefully they can understand we came here with a game plan and got a result. We got the one so we can look onwards and upwards now."
Sunderland looked a surprisingly strong team unit considering the number of transfers in and out this summer.
Di Canio has so far signed 11 players and more are on the horizon, but, while still a work in progress, Gardner has been impressed by the early signs.
"We work day in, day out on the training field," he said.
"Each game comes and we have got a different tactic to approach the game and - only time will tell but - I think we will be fine."