The Bluebirds spent over £30million in the summer as they brought in reinforcements ahead of their first season in the Premier League.
Steven Caulker, Gary Medel, Kevin Theophile-Catherine and Andreas Cornelius were among the players to arrive in the summer, with the first three of those acquisitions proving particularly successful.
Cardiff's January recruitment is likely to be in the spotlight after the departure of Iain Moody, and his replacement Alisher Apsalyamov's visa issues.
But Mackay is confident he will add a defender, midfielder and striker of the right quality to his squad to bolster the Bluebirds' survival hopes.
"It would be great if we can bring in three quality additions to the squad," said Mackay.
"I would look to strengthen all three departments in terms of a defender, a midfielder and an attacking player."
Mackay also praised the club's board for the backing they gave him during the summer, and is awaiting guidance from them as to how much he wlil have to spend next month.
"I will talk to my chairman (about January) who will then discuss it with his board of directors and our owner and I will take my lead from them," he said.
"It's up to them then what financially they want to spend in January. I've got my lists of players, whether they be permanent targets or loans for various positions. We've got to try and strengthen again.
"We are a first-time club so to speak. Everyone barring two other clubs has got a massive head start on us in terms of quality.
"They might only need to bring in one or two over a season. We had to bring in a group of eight players which was going to give us the chance to survive.
"You have a choice, do you invest knowing you have a really good chance of staying up or do you invest knowing you might go down and then have to build again.
"I was offered the chance to allow us to stay up. Looking at two or three players right now, without picking anyone out, but Theophile-Catherine has been a fantastic bit of business for us as has Gary Medel and Steven Caulker.
"January is about now putting another layer on that. It's a different type of window though and you have to be careful.
"There's not quite the array of talent out there in January and people are leaving clubs for different reasons and overall you have to be careful. It's about bringing in another layer of quality to add to what we've got. I need to bring in guys who are going to add to that."