Need help with my hair.?

Okay so whenever I wash my hair it always poofs out, I normally straighten it and then it just gets all frizzy. I use the Aussie shampoo and conditioner. If it's any help I usually wash it at night and I don't blow dry it because that makes it frizzy and poofy. my hair straightener is a purple conair one. also I just noticed that I have dandriff how can I get rid of it and how can I stop my hair from poofing out???? (without making it frizzy)