You should definitely moisturize your skin.  Moisturizing your skin keeps it young, it actually helps your skin not to overproduce acne, especially if you keep it light, it stops certain pores from getting clogged, and it helps in various different ways.  However, you should never combine your moisturizer and foundation.  By that I mean they should be in separate bottles and separate products.  First apply your moisturizer, and then apply a dry foundation to that skin.  If you use a combination, it is far more likely to be heavy and actually cause greater acne in the process by clogging your pores.  However, if you use them separately, your moisturizer and foundation both can actually have extra acne fighting ingredients.  Oftentimes, some moisturizers use green tea, tea tree oil, and otherwise while I’ve seen at least one foundation using salicylic acid.  So if you combine these together separately, obviously you could get the combined benefits.  However, again, stay away from them combined, which would in a way be the definition of for example liquid concealers.  And frankly, I would highly recommend that you actually use bare minerals, which are really good for the skin and pretty light as well, which definitely helps.