The Bluebirds manager reportedly has £25m to invest and is mulling over which areas of his squad to strengthen ahead of the new term.
"We're going to plan properly and that's started already and we'll now put that into action," Mackay told BBC Sport.
"We'll make sure the departments we've opened up at the football club and the structure we've implemented keeps striving forward. Change is constant and, if you don't go with it, you're left behind.
"We've been changing and adapting, pushing the envelope and trying to get the best practice in every avenue we've gone down. We'll continue that to make sure we give ourselves the best chance we can in the Premier League."
Cardiff secured promotion to the top flight with Tuesday night's 0-0 draw with Charlton Athletic, but are yet to wrap up the Championship title.