If your hair isn't too long and you have good water pressure, rye flour can be a really effective shampoo. I understand it sounds kind of kooky but it's ph balanced and gently absorbs excess oil without stripping it from hair. I have thin, fine textured wavy hair that's extremely prone to frizz and I used to walk around looking like I had a Van der Graaf generator in my pocket. I swapped to using rye flour and cut my hair short and now I love that my hair has cohesion to it and it's so so soft. Cons of rye flour would be that it can be hard to rinse out completely and it can make a mess with little flakes left in the shower or on a towel. It's also a bit weird to use because you need to turn it into a sort of paste as you wash, so you can't prepare it beforehand. Anyway, it might be worth a try if you're looking for something gentle, but you might still want to only rinse your hair every other day to avoid stressing it.