Here's the deal. If you are like most women, you have yellow-based skin. Most foundations have a pink or orange base. Even though you test and test and get the right depth of color, it will never match because the undertone of the foundation is wrong. This is why you end up looking cakey and two-toned.
If you are blessed with naturally flawless skin, use the sheerest liquid foundaion you can find. The small level of pigmentaton in the product, will mimimize the problem. If you need coverage, you must use a true yellow based foundation to align with your natural undertone. I have seen women use yellow-based camouflage foundations (with maximum coverage!) and didn't look like they were wearing a foundation. They looked as it they had naturally flawless skin.
Hope this helps.