Fade is a unique style statement that is compatible with your personal style. This makes it impossible for someone else to put a number to your preference. The number of layers to fade haircut depends on the length of your hair, thickness and the final look you are aiming for. However we can help you with a basic estimate for the same.
So let us start with thick hair. If you have thick hair then you need more layers so 3 will be your minimum. This is the only way you can make your fade visible through the thick growth. But if you have thick curly hair then you might want to skip this style all together. It will not be visible or effective in the manner it should be unless you are trimming all your hair short.
If you have scanty hair then you might want to opt for lesser layers of fade and also start the fade lower than usual because otherwise you may end up looking midly bald.