I know a lot of people here probably hate formal education. Still it's good to broaden your mind. So what would it be? Accounting? My CPA handles that, so that's probably not for me. Legal issues? I have a lawyer. Might be worth it to drop a grand or two on a course from a university.
Depends on what skills you are wanting to develop to enhance your career. IF you think knowledge of technology can help you take an introductory class to technology. If you think you need help to manage a business, take a business management class. Study it out and see what you think will better yourself.
I don't believe in formal education. I don't have anything against classes. I just think that experience is much more important, and anyway the best would be to have both of course.
I would take a class in which i would be able to learn entrepreneurship skills and abilities to better enhance the views on how the company I will work for came to be. Having this knowledge will help you be self sustaining even if you lose some of your money.
I would attend the Million-Dollar Entrepreneurial Master's that Amit Mehta from Boost Software gets to attend.