Cellulite is caused by the way fat and fibrous tissue are organized. It's a natural way for the body to store superficial fat. Most women have cellulite at some point in life. It can affect children, babies and even men.
The causes can include changes in metabolism, physiology, eating habits, sedentariness, alteration of tissue structure, hormonal imbalance, genetic factors, etc...
first thing is... if you want to improve the appearance, you need to lose some body fat. Good nutrition and strength training can do magic for you body. Try it!
Creams, massages, pills... all are scams.
There's no magic, there's work.
However if you're already lean and have cellulite, I'm sorry to inform you that cellulite is far more genetic than diet only. Cellulite has much more to do with elasticity from your skin and the fibers that bind the skin to the muscles. The more flaccid, the greater the irregularity of the adipose layer on your skin. That's why we often see lean girls who have cellulite and fat girls who haven't.
The only cosmetic procedure capable of removing adipose tissue and lose skin is liposuction and plastic surgery.