I'm having trouble beatin Elite 4 on Pokemon Diamon, help me build a team?

I struggled with beating Cyrus, but managed... I tend to pick and plant berries and explore underground before extensively training my team. I would like to hear suggestions on which *type* of Pokemon I should use which would benefit most.. ie rock, psychic, water.. you know? Once there I could work harder on training the Pokemon that have a chance. I'm very willing to work at this :) What Pokemon did you use, any suggestions?