Dandruff or Product Buildup??????

My hair is so dirty all the time. I washed it yesterday and it has so much dandruff or product buildup i don't know which one. i rinse, put shampoo, rinse, dry completely, and then i put conditioner, and brush. My hair is very different and extremely tangly and curly. What do i do to get rid of all the dandruff or product builup???????? plz answer. thanks!!!