@Rushtush Revlon and Essence are where it's at. There's also a brand called Modern Dollz on IG that has a larger range of pallettes that look good and are affordable
As a make up artist you may not always have a wide variety of foundation shades or a shade that matches a client. In these circumstances you have to think on your feet and mix foundations until you have the right shade.
The natural reflex is to mix these on the back of your hand, but your hand only has so much space. This is when a mixing palette comes to your rescue. A mixing palette helps you mix foundations, concealers, lipsticks etc until you get the shade that is to your preference.