I have almost all the necessary colors in the Copic Sketch 72A set of markers, but if you want to put together the perfect palette, then you should buy a few more markers of white skin color (in my case), that is, light earthy shades. I studied swatch and drawings all evening, and for myself I chose the following shades:
E00 (a typical light beige shade for a light skin color, goes a little pink), because in my set there are already E15 and E33, then together we get an excellent group for rendering the skin. With this choice, we will compile a complete set of Earth, covering all tone preferences.
E50 (light flesh, slightly lighter and more beige than E00), can be used independently, or for illumination. It makes no sense to choose a tone even brighter, since on white paper it will be difficult to see the difference. But if you want an even lighter shade for the collection, I would stop at the YR30 (this is a very lighter shade for almost white skin).
You should definitely take the midtones that are not in the Copic Sketch 72A set — these are E04 (warm light brown with a wine tint), E70 (neutral light beige), R00 (very light pink, often used for blush on light skin) , V000 (warm light violet with a noticeable pinkness) and V91 (a tone close to E70, but more violet).
This is a necessary minimum for comfortable skin painting, I took myself even more missing shades, but they are not so necessary. Here are all the shades I bought for my Copic Sketch 72A set: