4 batteries will not effect how you build it. Do you know what kind of battery:AA AAA 9V C D?
An LED provides light, it can be used for line-following in the dark, or signalling something like if a motor is on. IR LED's can be used for wall avoidance.
Does the robot or the statue have to have a charecteristic?
Do you have any prior knowledge of Electronics, Programming, or Mechanics?
As waltr said read EVERY tutorial, I almost have. They are very helpful. Make the $50 robot, and then maybe scrap the parts so that you can build your robot with the same board.