i consider CPA to be a micro-earning, and even less when it comes to CPA in bitcoin. the time and effort that takes to do the "action" to get paid is not compensated by the amount you are being paid. not to mention the bitcoin CPAs are not that good yet.
i suggest trying "freelancing". for example if you have any skills then offer them for doing jobs, they can be small and get paid in bitcoin.
How can you ever say this ? There are some people earning more than $20,000 from cpa account every month, a good example is the former owner of the angry bird game who was earning over $50,000 daily with his in-game cpa.
This all depends on what you know and how to manipulate things unlike freelancing that waits for job which is has a lot of competitions.