The only ghost Pokemon in the game is Haunter, which gets no special STAB and is worth using only if you can trade and evolve it and you don't already have a poison Pokemon on your team, like Ivysaur. I also think Dragonite evolves way too late to be worth the hundreds of thousands of experience, so I recommend that you stop using Dratini and Persian and not get a Haunter so you can put all your experience into your stronger Pokemon. If you really want a team of 6, then I think you should use Zapdos and Clefable instead of Dratini and Persian.