One must wash once face, the minimum number of times that one should wash the face would be twice, once in the morning and once at night. The type of cleanser that is used usually depends on the type of skin that you have. You may have oily skin, a combination type skin or a dry skin. If you have dry skin you must use a very mild foaming face wash and if you have an oily skin you can use cleanser that have a salicylic acid or benzyl peroxide that can control the sebum.
And it is essential to exfoliate the skin once every week or two weeks because washing the skin essentially removes the debri, the make up from the previous day or sebum that has accumulated on the skin. So throughout the day your skin secretes oil and you sweat and it’s important to take all this debris out and cleansing helps to do that. It also prepares you for the next step which is moisturising the skin and you can moisturise your skin depending on the time of the day.
During the daytime you can use a moisturiser with certain active ingredients like vitamin C or E and at night you should use moisturisers with different sets of active ingredients that will work through the night. It will really prepare your skin so that the skin absorbs these ingredients. It is important to wash the skin at least twice a day but if you have very dry skin then you can get away with washing your face once.