A question for makeup lovers and gurus...?

Okay- I need mega help: my makeup looks absolutely disgusting , caky, and sunken into my face by midday. MIDDAY!! I cant take it any longer- I want to look fresh faced, and neat, not like one of those girls who cakes on the makeup! This is my current routine: (oh, and I should mention that I am taking doxycyline 2x daily, and using SFC {Soap free cleanser} with benzoyl peroxide/clindamycin in the AM and differin at night to help treat my acne: all prescribed by my derm.) But here's my makeup routine: Cover Girl Natureluxe foundation, CG fresh complexion (they obviously should find a new name for it...) concealer, Physician's Formula powder, and Physician's Formula Plump Potion mascara. My face also flakes, it is kind of dry, but I have been skimping on moisturizer, as my derm advised me to use as little as possible... So. Yeah. Please help me! I hate the way I look by my third hour class, and it really brings down my confidence! :( What are some good, inexpensive makeup products that are nice, and not crappy?? Thanks, it is much appreciated!!