If I were a millionaire, my lifestyle wouldn't change. I would still go to work, although I wouldn't have to worry about money. I would also spend time with my family and hang out with friends. I'd work hard to enjoy a meaningful life and continue to contribute to society.
If I were a millionaire, I would buy loads of books to read. I'd also take as many extra lessons as I could, because knowledge is power! I wouldn't spend too much of my money on luxury items, but I'd probably travel around in an air-conditioned limousine.