Going for knowledge just because it sounds cool isn't going to be a motivator strong enough for success. Find stuff you're interested in and dive into those. The way to become a well-rounded person is to become obsessive in many things (possibly not simultaneously) that are unusual in some way. In fact, learning anything will feel like specialization, and in fact being a serial specialist is probably the most viable way to become a "Renaissance man" today.
Note that the first thing that came to my mind when I read your post was: "To be a true Renaissance man, you need to have been dead for 400 years". I won't write it here :)