The Sweden striker pulled a goal back from the spot after Christos Tzolis was fouled by Jobe Bellingham, but Borussia Dortmund held on to win the pre-season showpiece at the Emirates, with Arsenal salvaging some pride by winning the subsequent penalty shootout 5-4.
"I think we created some good chances, probably could have scored in the first half from a few of them and then I think, of course, we have to do better in those moments where we concede," Gyokeres said.
"I think the same goes in the second half where we concede from a corner, a bit unlucky but still we need to do better. I think we have to make sure we don't concede those and then of course we managed to score two goals in the second half but there's a lot to do better."
Arsenal trailed 2-0 at the interval to goals from Samuele Inacio and Konstantinos Karetsas, before Ethan Nwaneri and then Gyokeres reduced the deficit either side of a third Dortmund goal from Joane Gadou.
Gyokeres also reflected on the influence of Martin Odegaard, whose return from injury offered glimpses of his understanding with the Sweden forward and Kai Havertz in the opening exchanges.
"We didn't play so much today together but in the first 20-25 minutes it felt good," Gyokeres said. "His movement is easy to see and then to adapt to and I think we played a lot of games now together, so it felt good."
Like several of his Arsenal team-mates, Gyokeres endured a demanding summer at the World Cup, but said his conditioning was in a far better state than 12 months ago as he prepares for a first full season at the club.
"I feel much, much better than probably last pre-season," he said. "I've had more weeks now and it feels very, very good physically."
Sunday marked Arsenal's first appearance back at the Emirates since they were crowned Premier League champions in front of their own supporters, and Gyokeres said the occasion, result aside, had been a special one.
"It was amazing to be back and to feel the atmosphere and see the fans again but of course we wanted a result as well," he said. "I think we're in a good stage, everyone is coming back now from the World Cup so I'm sure we're going to be ready for everything that comes."