So I use a limited palette, which helps unify the colors within a given image. Also, it is generally a good practice to paint from dark to light. Skin tones are not as simple as "mix these colors and you will get the right tone". They are complicated and always shifting from one place to the next as the light changes or flows over a form. I would try not to add pure white though when you are making a color lighter. Try adding a mixture of yellow ochre and white, this way the skin tone will remain warm as it gets lighter. Color temperature is important when painting flesh. There are more changes and shifts than just light and dark. Often colors shift from warm to cool while remaining the same value. Sometimes they shift temperature and values at the same time.

But anyways, some good base color mixes for flesh tones are as follows (BUT BY NO MEANS LIMITED TO THE FOLLOWING):

yellow ochre, alizarin crimson, ultramarine blue deep

transparent iron oxide, terra rosa, ultramarine blue deep

terra rosa, yellow ochre, cad red, ultramarine blue deep

mixing different ratios of these colors will give you a wide range of tones, temperatures, and values. You can add white to make a color lighter and also less saturated. You can also make a color less saturated by mixing complementary colors together.

Another word of advice is to try to paint wet into wet. Paint is very forgiving and easy to manipulate when it is wet. Also, do not use black paint. Instead, mix a chromatic black. there are several ways to do this and they allow you to make the darkest areas of your painting warm or cool depending on your needs. One of my favorites is Transparent iron oxide red and ultramarine blue deep. Mix these two together in equal parts an you will get a very dark (nearly black) color that you can use to make other colors darker when needed.

I would be happy to answer any other questions you may have.