Makeup base is used to correct the imperfection for your skin tone. Whether there is a need on putting makeup base before applying makeup depends very much on individual and their complexion. If their skin is very dull, red and patchy, dark eye circles, the usage of makeup base would greatly help in enhancing their skin.
Makeup bases comes in different shades for different skin problems. A purple base will provide radiance for dull looking skin while a green base will reduce redness as for yell0w or ivory base make will make skin look smoother.
Makeup base also let your makeup last longer and fresher.
I would suggest oily skin type use Light emulsion for sebum control and Creamy base for dry skin as it will protect skin from dehydrating.