There is no better way to master robotics than building and programming your own robots. If you are looking for an inspiration, you may want to give SmallKat a look. It is a project all about building a cute robot cat. It is a low cost 16 DOF 3D printed robot cat with an ESP32 module and a BNO055 IMU.
The above video shows SmallKat in action. You can find out more about it here.