There is no better way to learn robotics and electronics than building your own things. Arduino is a wonderful platform to rely on to get started. The RobotGeek Whegly is a wheg robot kit with 4 whegs that can negotiate rough terrain. It can go from rolling to climbing fast.
The kit comes with a RobotGeek Geekduino, 4x RobotGeek Continuous Rotation Servos, and a rigid 1/8″ thick Delrin body. Its 2200 mAh battery lasts up to 2 hours.