I went from a head full of dandruff to zero in four years. It requires you to control your food intake (reduction in oily, spicy and junk food), regular shampoo with a gentle, dry-hair shampoo, and regular massage. Oil helps, but only to lubricate the head while massaging, it doesn't actually do anything for the dandruff. A light, chemical- and additive-free oil works best for this, Vatika is a decent choice.
Oh, and a weekly head rub with curds and ground pepper, and soft water for a bath. Hard water exacerbates dandruff like there's no tomorrow. If you have oily hair and dandruff, it gets more complicated and you have to take treatment for it.