Most people in our society use shampoo multiple times a week, and they have always done so. Here, I suggest the unthinkable: Don't.
Half a year ago I discovered this idea that the internet labelled No-poo. Many just wash with water and let their hair do its thing; others add non-chemicals such as lemon juice. I personally only know one other person not using shampoo, but it appears that most who do still have perfectly beautiful and non-smelly hair.
I haven't been using shampoo myself and, after a little time, my hair has been as presentable as ever. My girlfriend agrees! One less thing to buy, carry and worry about. Faster drying hair. Less stinky perspiration. No greasy hair if it hasn't seen shampoo for a few days.
I can only say what others have been saying for years: Try washing your hair without shampoo and see how it looks after two months.