This might be common sense to many... But it definitely wasn't one to me! So I have been using nyx eyeshadow base.
And it's an amazing base because it's white so any color you apply to your lid pops. However when I watch YouTube tutorials people applied the base and would go straight to eyeshadow. But when I did this I found that there would still be a visible crease.
I tried putting eye shadow primer ontop of the base and that solved my problem. So base, primer, eyeshadow in that order! Xoxo