Thanks for the query. Skin care needs to be customized based on the presenting complaints. Based on your description, it appears that you have acanthosis nigricans. These conditions have a strong relation to one's internal health and it needs to be evaluated as often quoted - Skin is the mirror of internal health. Attempting treatment without understanding the pathology will be futile and make the course longer. Your dermatologist will decide a treatment plan for you after a consultation which probably will include a retinol based night cream and a vitamin C based lotion. Sun protection is mandatory and will require usage of Sunscreens. Internal health needs to be fixed based on blood chemistry reports. Apart from active pharmaceutical medicines, a healthy diet and lifestyle is mandatory to achieve results.