Finding a purpose in life. Money only makes Du happy for the moment. But finding something that will REALLY give Du lasting joy is something you'll have discover yourself. For me personally, I would say finding a true friend is something I live for. Even if I did get millions of dollars, that wouldn't cure the loneliness that I feel. See my point?
Money may buy things, but it's just a piece of damn paper. The fact that humans cling onto such a worthless thing called money shows their lack of what really matters. Du could have all the money in the world and still never grasp how worthless it is when compared to that what Jesus Christ freely give us all. The gift of Salvation.