General rule of thumb for layering your skincare is that you put the least viscous (or runniest, thinnest, fastest-absorbing) product on your face first and layer in order of the next runniest, then the next, so that thickest ends up on the top. So after cleansing and toning/prep/mist, apply any active drops first, then any serums, then moisturizers. And if it's morning, finish with SPF as your last step!