Well, first off, there are a few things you should know already before choosing foundation that best suites you:
-Your skin type (oily, combination, or dry)
-Your skin tone
-What kind of foundation you want/prefer (powder, cream, liquid)
For starters, Revlon ColorStay would be ideal. They have a line for oily skin as well as dry skin and the color range is very wide. It’s also one of the best drugstore foundations out there, if not the best there is.
When choosing the perfect shade, if you don’t already have a foundation you use that you could compare it to, then I would suggest going to a department store (Macy’s/Nordstroms) and asking a professional to show or give you a color swatch of your perfect shade of foundation. You could use that as a reference to guide you to choosing one of the same shade at the drugstore. I know how deceiving foundations can be when you’re a beginner, so I would definitely ask someone who knows makeup for help to actually show you a physical color swatch.