We needed to determine a basic skin tone for our picture. Below shows a chart I made once in a workshop. Each block has a mix of two basic colors (such as raw sienna and permanent rose), then shows what it would look like with a third color (sometimes a fourth) charged in. Sorry these really don't show up well.
For example, the first square is raw sienna and permanent rose with Janets Violet charged in. Second in top row is naples yellow + permanent rose with Janets Violelt. Third is coral + green gold. Last in the top row is quin burnt orange and green gold. So experiment with colors - usually one from the yellow family+one from the orange/red family+a surprise, like veridian, hookers green, Janet's Violet, or verditer.
Think of it like this. If you are baking, you can take four ingredients: flour, sugar, salt, and baking powder, for example. From this BASE you can make a number of things--muffins, bread, cookies, cake, donuts--OK I'm making myself hungry. But you get it. We simply add more or less of one of the ingredients and sometimes other ingredients to make what we want. But the base is pretty much the same.
So make a BASE color that seems close to the skin tones. Then add more of the red family for rosy areas, the addition of a cool for shadowed areas.