A levitron requires two magnets. It's like putting a south pole and a south pole of a magnet together. However, it is additionally stabilized by angular momentum (the spinning of the top). Otherwise, like putting a south and a south together, it's not stable and tends to fall. There's something a little more complicated involved, but that's the basic idea. The earth's magnetic field is so weak that it is highly unlikely you support any sort of other magnet in it.