I would suggest either scrolling a texture across the tracks (common), or if you want more detail, give each tread a bone and animate it.
A hint on tread animation: You only need to animate each tread moving one unit forward, aka, tread 1 would move into tread 2's spot, and tread 2 would move into tread 3's spot, ect. If you can get each tread to move into the exact position that the previous tread was in, and then loop those frames, it will
appear as if the treads are going all the way around. I used this trick for a really simple tread setup, but it should work with more complicated rigs as well.