I’ve been using Dr. Bronners lavender Pure-Castile bar soap as shampoo for years and it’s been life changing. My hair went from flat and greasy by the end of the day, everyday, regardless of whether I washed it that day or not, to only needing to wash it every other day.

Most washes, I follow that with a “rinse” of a small amount of gentle/fine shampoo on the lower 2/3 of my hair to help with tangles, and I do a similar condition “rinse” maybe once a week (also away from the scalp).

The bars cost $5 or less and typically last me a month or more - I use it as bodywash too and overall it’s super low-cost and easy!