I'm worried because I have thin hair.

Ever since I dyed my hair, it has grown curly and lost its strength. So, I hadn't gotten a perm or dyed it for about 10 years, but when I dyed it again, the hair grew back even weaker and thinner. It grew up messy and unkempt from the roots, looking like dog fur. That made me realize that the more damage you inflict on your scalp, the more damaged your hair becomes. They said the hair roots themselves were damaged. I spent millions of won on hair treatments, but they had little effect, and I ended up with the thin, weak, and sparse scalp I have now. Are there any treatments available to help maintain a healthy scalp? If so, please recommend one that is easy to do in terms of price and cost-effectiveness.