Track to your goal, not to vanity. For awareness, watch reach, impressions and engagement rate. For consideration, clicks, saves and profile visits. For sales, trackable conversions through promo codes, affiliate links or UTMs, plus cost per acquisition. The number that lets you compare creators fairly is cost per result, whether that result is a view, a click or a sale. Skip raw likes. Set the KPI before the campaign so you actually know what you are measuring against.
Match KPI to goal
Awareness, consideration or sales each have their own numbers. Pick first.
Make sales trackable
Promo codes, affiliate links, UTMs. If you cannot trace it you cannot prove it.
Use cost per result
The fair way to compare creators. Cost per view, click or sale, not follower count.
Set it before launch
Decide the KPI up front or you will rationalize whatever happened after.