Thanks for writing here.
Dark pigmentation can be due to hormonal imbaalnce,sun exposure,cosmetic allergy
Start applying a good sunscreen at day time.
Apply a combination of kojic acid
and vitamin c at night time and a mild steroid like hydrocortisone
at day time.Use steroid only for 1 to 2 weeks..
Avoid facials,since they may produce further darkening.
For oily and dry skin you can use a good cleansing lotion.Cetaphil cleansing lotion is one which is used commonly for such purpose.You can also consider to visit a dermatologist
and go for chemical peel.
I hope this will solve your problem.Take care.