There is no better way to learn electronics than playing with Raspberry Pi and Arduino. CarmelitoAndrade has published a guide that shows you how to build a toy truck powered by a Raspberry Pi. It has 3D printed parts, a power bank, and an Adafruit DC and Stepper Motor HAT. You can use your smartphone to control the truck.
The above video shows this smart toy truck in action. You can find more instructions here.