When it comes to applying makeup, it is generally recommended to apply moisturizer before primer. This is because moisturizer helps to hydrate and prep your skin, making it smoother and more even in texture. Additionally, moisturizer can help to create a barrier between your skin and the makeup, helping to prevent the makeup from clogging your pores or causing irritation.
Once your moisturizer has had a chance to absorb into your skin, you can then apply primer. Primer can help to create a smooth, even surface for your makeup to adhere to, and can also help to extend the wear time of your makeup.
So, the general order of application for makeup would be:
Cleanse and tone your skin
Apply foundation and other makeup products as desired.