Don't worry about taking the foundation courses (in my view it would be a waste of time and money if you're looking to do an MBA -- also, it won't really help your chances).
Keep in mind that the MBA curriculum isn't really "advanced" -- the first year core courses are essentially 100-level type courses. In other words, they are "survey" or "intro" courses that teach the very basics and foundations of the subject, assuming the students have zero background on the subject.
For example, the accounting class in your 1st year will be an intro to accounting class, starting from the very basics. Same with economics (microeconomics and macroeconomics), and so forth.
If you really just want a very bare bones or basic knowledge before entering school, you're best off going to Barnes & Noble or Amazon and picking up those "Portable MBA" books.
In the meantime, just focus on the GMAT because your score on that will have a much larger bearing on what kinds of schools you can get into more than anything else at this point.
Follow me on Facebook