Diamond Expert

This event rewards you for spending your diamonds. You will get 1 point for each diamond you spend, making this perhaps the most nonsensical of the events.
Unless you are spending your diamonds anyway: healing, speeding up training, or research or spending them in a way you would normally spend them, ignore doing this event.
To reach phase 10, you will need to consume 45,000 diamonds. Along the way you will earn a fraction of the diamonds you wasted. This is probably one of the least economical events, and its just a sink (a way to get you to spend your diamonds so you will need to purchase more).
A lot of games use this tactic to get people to spend more money. While being a black sheep is cool, being one of those normal ones is not, do not be the other kind of sheep and do what they want you to do. Save your diamonds for other things.