Simple answer: Get the FULL KIT - it includes everything you need to assemble a robot, you don't have to 3D Print any pieces yourself.
Complex answer: Get the Maker Kit - 3D print the robot at a local facility which has 3D Printers available for you to use! If you are a student, most schools / universities / colleges have 3D printers available. Alternatively go to your local makerspace! Incomplete list of 1000's of makerspaces worldwide : http://themakermap.com/
We've tested it up to 750g whilst walking for the prototypes. While stationary it can handle up to 1.5kg, but can't walk properly. The more weight there is added, the quicker it will deplete the battery charge.