My app is a subscription based app.
I have about 300 subscribe events logged and attributed to a particular ad from the last 60 days.
The app has 3 day free trial period, and trial events are logged as StartTrial, and Purchase (and yes, one trial is logged twice under two different event names). Event count for each of them is over 2,500 for the last 60 days.
When I run ads optimized for Purchase, I get satisfactory results. But not when I optimize for Subscribe.
I have a feeling that successfully optimizing for Subscribe event will improve the free-trial-to-subscription conversion value, so I am very eager to make it work. And I think it has not been successful because of the low event count. Please correct me if I'm wrong.
So my question is, how many subscribe event would I need to run a successful ad optimized for it?
Or it is just the case that FB ad works well with Purchase optimization but not with Subscribe optimization?