I believe it is worth mentioning that washing your hair more often because of the dandruff can be counterproductive. Most shampoos are quite harsh detergents that also remove all the good stuff from your scalp that keeps the skin and hair healthy. If you wash your hair too often you dry out the skin and encourage it to get greasier more quickly because it is trying to counteract the stripping of oils by the shampoo.
One thing you could try is to reduce the frequency of washes. It takes some time for your scalp to adjust, but after a while it will produce less oil.
What I sometimes do, is I massage some oil (my favourite is coconut, but you can use olive/almond/etc. as well) into my scalp and onto the ends of my hair (they tend to get frizzy) some hours before I'm going to wash my hair or leave it in over night. An egg mask is also a low-budget, less harsh way to treat damaged hair (this is just one exemplary recipe).
Generally speaking, I would not suggest to put more stuff onto your scalp and hair, as this might dry out your hair even more.