In my experience, dark circles are due to lack of sleep. Start getting at least 8 hours of sleep everyday and you should see good results in a month. Another factor is hydration. Drink lots of water and fruit juices too. Don't rub your eyes. Get your eyes checked for a refractive error. Depression can also cause dark circles... consult a psychiatrist if that is the case.
None of the creams available in the market can help you if you don't consider making these small lifestyle changes.
Dark circles under eyes are due to allergic conditions, strain on eyes or outdoor job..majority of these have no satisfactory treatment and even after taking a cumbersome and expensive options, results r disappointing, just follow few rules, don't rub eyes much, apply light make up around eyes, don't do any make up while going to sleep, in fact take a nice wash on face with soap before going to bed, take a good sleep for at least 6 hrs in night, if you hv to work on PC for hours, start some lubricants.. There are many cosmetic options in market but believe me, they r useless.