Foundations are really tricky. first you have to find the right shade then after finding a shade that matches you have to make sure that it's the right foundation for you
I was "Blessed" with very oily skin, so it's hard for me to find a foundation that works for me... the one i have found is Revlon's colorstay oily/combination formula
but how do you know what skin type you are? here are some hints
if after 2 to 3 hours after washing your skin has a sheen to it you have oily skin, if after the same amount of time passes and you just have an oily t-zone you have oily-combination skin if in the same time frame passes and nothing happens.. lucky you. you have normal skin if you notice any flaking you have dry skin.. it's not hard to figure out..
if you have oily or oily combination i would recommend Revlon Colorstay or Makeup forever's Mat Velvet+ depending on your price range... and make sure you pick up a setting powder... with normal or dry skin i would go with something like Nars Sheer Glow or Neutrogena's Healthy Skin Liquid Makeup or Covergirls Nature Luxe. Application is also tricky... my experience with conventional foundations brushes is not a good one.. it cakes it on and makes ones face look extremely streaky and uneven... go with a sponge or a flat top kabuki or my favorite my fingers. your fingers are going to make the product melt into your face better and give you a really nice natural finish just make sure to have clean fingers! I hope this was helpful and if you have questions feel free to ask and i will answer as best as i can... :)