There is no better way to learn about robots than building and programming your own robot. This project can give you a few ideas. This 6WD All Terrain Robot has a ground clearance of 45mm and weighs 5kg in total. It is built with 6 x 180RPM DC motors, Arduino Mega, 1:10 Monster Truck tires, and a few other simple components.
The extended version has a RunCam split camera, 2-axis gimbal, and a robotic arm. You can find out more about it here.