Look at Making Cuts for some cues on how to cut effectively.
Why do we recommend throwing the diagonal throw to a diagonal cut? This drill is about reinforcing cuts into one third of the field - ideal for continuation cutting and split stack / side stack offences where you can expect poaches from the far side of the field.
Avoid making changes of direction here, just commit to your cut. It's as much about training the thrower to recognise and hit the option early as it is about getting open. That said, the best method of adding motion is to begin with a lateral cut; see Engaging Defenders