Buy 3 varieties or buy 1 and keep using what you have already been using as well.  Shampoo is a funny thing.  And what Ogleby recommends is that you switch up your shampoo types a few times per week.  Sometimes switch up by shampooing twice in the same shower and using a different type.

All hair types - berry

All hair types - delicious citrus

All hair types - peppermint tea tree

Fine hair - coffee

Oily hair & scalp - pure hydration

Shampoo