Start with the conversion rate, not the bid
Cost per action is a function of media cost and conversion rate. Improving onboarding completion or store-page conversion often reduces CPA faster than any bidding change.
Rotate creative deliberately
Creative fatigue inflates costs gradually and is easy to misread as a media problem. A planned refresh cycle, informed by performance decay curves, is cheaper than an emergency rebuild.
Prune sources honestly
Source-level reporting almost always shows a tail of placements delivering volume without downstream activity. Removing them raises average quality and lowers effective CPA, even if headline install counts drop.