I hardly use any foundation (although I should, just to even it all out). I usually just swipe on lipstick and I look completely made up. Only when dressing up do I wear shadow, liner, and (rarely) mascara as well.
I usually wear full makeup every day that I leave the house. I don't feel I have the best skin so I feel naked if I'm not wearing anything (and I'm a makeup junkie too). On days I don't plan on going anywhere I usually don't put on any makeup.
I usually do a powdered foundation, blush, finishing veil, and occasionally I'll throw in some eye shadow and mascara. If I'm going out or going somewhere where I'm dressing up and "getting ready," I'll do full makeup.