Math Major ok GPA struggling with cases

2 main questions :

1. If someone has a lower GPA for consulting (3.35), but is in a very rigorous math program with loads of leadership stuff on the resume, what are the odds of landing an interview with MBB at a target school? Would chasing second tier consulting firms be a better use of time?

2. As a math major with no business experience, how does one become familiar with basic business concepts like vertical integration or operating margin? Not knowing this stuff has been a major stumbling block doing practice cases, so does this just come with more practice cases or would reading an accounting textbook or something help more?

Thanks in advance