For a healthy and shiny look, try to avoid using cheap quality products because using these products is as harmful as pesticides to crops. Weekly oil your hair and use a branded moisturising shampoo and conditioner. Using a good quality conditioner is better as it will not only prevent any more damage but it will also help to make your hair healthy. Always buy a shampoo according to your hair type I-e oily, dry etc.
When you wash your hair avoid using hair dryer. For dandruff, I recommend you to use coconut oil as it will reduce dandruff in your hair. Other than that, you should use different types of hair oils available in the market but you should analyse their performance on your hair for at least two weeks. As I have mentioned before, that dandruff can be one of the biggest problem in damaging your hair so if your condition persists then you should visit your doctor or skin specialist as soon as possible.