My general experience with the GRE is that it skewed heavily towards multivariable calculus, since it's the one 'advanced' topic that you can pretty well guarantee that all undergraduate math students will have encountered. Upper level courses already diverge into analysis, groups, combinatorics, and more, so you can't really make a standardized test heavy on group theory, for example. So get damned sharp on your multivariable calc and you'll be good to go....

As for the bigger life direction question, I have no idea without further context.