For dry skin, opt for a light coverage, moisturizing foundation.
Try CoverGirl's Tone Rehab from Amazon for $11.55.
For oily skin, opt for a more medium to full coverage, matte foundation.
Try L'Oreal's Infallible Pro-Matte from Amazon for $9.61.
If you have combination skin, then you'll have to test out a few more samples to figure out which one's best for you. Read here for more tips on selecting foundations based on your skin type.