Not shampoo but I love the volumising spray from Davines.
Also recommend motor mouth vokumiser by Tigi.
As well as the volumising creme from Bumble and Bumble.
For a cheaper option, I like the sea salt spray by John Frieda.
I avoid volumising shampoos as they often have ingredients in them that coat your hair, every few days I use a clarifying shampoo to remove product build up. I use the Neutrogena one which is quite cheap. You shouldn't use it daily though.
For a cheaper shampoo I really love the Loreal Everpure range.