I always moisturize prior to foundation application. If my skin is being naughty, Ill add in a primer in between my moisturizer and foundation. This goes for liquid and powder foundations. Hope this helped.
I put on moisturiser after I get out of the shower, then get dressed, then I will sometimes prep with YSL Top Secrets Flash Radiance otherwise I simply mix my foundation in with Clarins Beauty Flash Balm and apply that mixture. It works well for me.