Any tips on frizzy dry wavy hair

My hair was so nice back then it was shiny and silky now it’s so dry and so frizzy And I even have an itchy scalp all the time, it’s gotten better over time but still no matter what shampoo I use it’s just always there still I even used treatment shampoo and they’ve done nothing And every time I get out of the shower and blow dry my hair or let the air dry my hair, my hair is just too frizzy like it’s horrendous to even look at and the next day it’s all dry again