I want a small, semi affordable, dolly just like this. It will be used just like whats being shown in the picture. Can someone point me in the right direction?
I can't help you with where to find one, but looking at the wheels it looks like the 90* skateboard wheel setup but off the tracks.
I would think using a skateboard dolly off the tracks isn't the best method... it will rough up your wheels.
Professional dolly systems usually have a set of pneumatic tires which are used for rough terrain as the dolly is in free roam mode (not on an aluminum or steel track).
You'll find that adjusting the inflation of pneumatic tires can let you calibrate your dolly to absorb rough surfaces or eliminate bounce.