Drink a lot of water. It naturally restores tension in your skin and makes it look bouncy and nice. (sorry that's a weird way to describe it lol but I don't know how else to say it). It also flushes out toxins that cause breakouts. Fruits and vegetables. Stay away from fried foods, some people say that's a myth, a lot actually has to do with how your body interacts with certain foods, but water and unprocessed foods are good ways to start. Exercise also, sweat out stuff in you system. There are certain foods (cant think of it right off the top of my head) that supposedly is good for your skin, google! And just natural care. Use face wash, not soap to wash your face, moisturize.
If you are naturally darker, then you can't make your skin lighter. But you can always make your skin smoother. Use a loofa and scrub 2-3 times a week. Apply moisturising body lotion or cream after showering. Use facial cleansing products and moisturise your face every day twice a day. Use under eye cream. Apply hand cream every night. Drink lots of water and exercise regularly. Eat healthy food.