Notice that it says "A Foundational Approach". You don't need a foundational approach to math to go through economics. Just get Stewart's Calculus (or Apostol's if you want to get deeper), and Strang's Linear Algebra.
Everything you need to know about logic/set theory can be learnt in less than 2 days. You'll develop intuition with time.
Also, probability, intuition and game theory should be your priority as
>>10153579 says.
