Is there a way to create stretch goals? For example, if 2 people the participant shared with purchase something on our website they receive $10, if 10 people purchase, the participant receives $50.

Unfortunately, our system cannot do this automatically, but it can be accomplished manually. This is accomplished by choosing a goal-based rewards campaign and setting the maximum number of conversions as a goal. Let's say this number will be 10 people. At the end of the time period, check participants' results and reward them manually according to their score. If a participant reaches 10 conversions, then he will receive a reward notification automatically letting him know he has earned the highest available reward.