The Cover FX Brightening Booster Drops ($32, originally $45) are a lightweight serum that increases radiance, improves skin's tone, and has earned 4.7 stars from other Sephora shoppers. And while there's usually a specific time to apply vitamin C, this product can go on under, over, or even be mixed with makeup to clarify and brighten, while included porcelain flower extract keeps skin hydrated as well.