It depends on budget and what your needs are. If you plan on gaming an APU is usually a waste.
As for the ratio, a 2.5 (2-3):1 ratio works fairly well, GPU:CPU.
So say you buy a 4690k, around 300 bucks, spend the money to grab something like a 290/780/290x.
This is not an exact science, nor the real way to go about it. Just a budget can help determine it for you.