This is just my opinion but those drivers feel too expensive for a first robot. If you have access to simple parts you can easily build an h-bridge to control your gear motors as long as they are not too large.
I'm in the middle of the same project and I found this design for an h-bridge which I really like for small gear motors. http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html
You connect it to three pins on the Arduino. One for forward, one for reverse, and one of the PWM pins to control speed. If you use two motors, one for each drive wheel (the recommended design for first robots) you need two of these, one for each motor.
There are a lot of similar designs out there and there are also integrated circuits which contain all of the parts of the motor driver in one package. As long as you keep it small you don't need to spend a lot of money on a motor driver (yet).