Is tgel good for your hair?

For dandruff, yes: T-gel is a very good tar based shampoo for the treatment of seborrhea, also known as dandruff. It is also good for itchy scalp. It can darken light colored hair, but otherwise it is very safe as directed.

Not on head: On your head i presume? No, if anything testosterone promotes hair loss there, hence why males have male pattern baldness.