There is no better way to learn robotics than experimenting with your own robot. The Hangfa Navigator Q2 Robot Platform is a premium robot that can move in all directions. The Navigator Q2 comes with four 45 degrees QMA-15 omni wheels and 4 coreless motors.
This robot also has a MOTC1 motor controller, RHF407 development board, and ULB-16 ultrasonic rangefinders. Not cheap though.