For a while, any foundation or concealer that I would apply to my face would either look cake, or flake-y. It got to the point where my boyfriend would complain to me about how my makeup looked, although I continued to wear it. D:
Eventually, I had solved the problem by switching to a new foundation. I had also started using a few other beauty products, which has been helping my makeup apply more evenly, and with less problems.
The new foundation that I am using is Revlon Colorstay. It's the best one that I've used so far. It's light, and provides good coverage, so you won't need to apply a lot, which means there will be less of a buildup on your face. I also use the Revlon Colorstay powder. They're both about $8 at Walmart. The concealer that I use is Hard Candy's Glamoflauge concealer, which is also about $8 at Walmart. This concealer covers imperfections well, and only a little is needed, so, again, less buildup.
As for my other beauty products, at night I apply a facial moisturizer after I wash my face with a facial cleanser. The cleanser helps to remove your makeup, and the moisturizer will help your face from becoming dry, which will help your foundation from becoming flake-y. In the morning, I wash my face with a facial scrub and a facial cleanser. This helps to smooth our your face, and remove any buildup that may have formed overnight from oil, dirt, etc., so that your foundation will apply on smoothly and evenly.
I haven't had any problems applying foundation or concealer since then, and my boyfriend is happy, as he says my makeup looks a lot better now. I think that one of my biggest problems was that I was applying too much foundation and powder, so be careful to not overdo it when you're applying your own foundation. I felt as if I needed a lot for more coverage, when actually a little bit of foundation would have done me just fine. Hope this helps. :)