Pokemon diamond team?

You have a bit of a weakness with the ground type with a few of your team members, ponyta, luxray. You probably want to get a water type. It's a pretty solid team though. Why not replace the meditite with the staraptor and teach haunter some psychic moves or replace haunter and teach meditite some good ghost moves. Gyrados is a decent pokemon but having him will increase your weakness to electirc moves since he is water AND flying. Maybe consider a different water pokemon on your team or teach Gyrados or staraptor some moves good against the electric type.