How often should you wash your hair? I feel like you want a balance between clean and not greasy but you dont want to dry your hair out. whats your methods?
Either or. You start by asking about gym hair care and then it sounds more general. Given the small variations between one person and the next don't base how often you wash your hair on the next person.
Wear a hat in the gym if you're worried about it getting grubby there. Clean it as often as you think it looks greasy. Google will probably tell you the average number of times and most bottles will recommend a similar number.
To be honest, my hair was the most soft and healthy when I did the "no poo" method. Literally just rinse with water. It sounds gross but if you read up on it and try it you will be impressed.