Actually I'm going to have a Psychic gym already, but Poison would be fine. I'm limited on my pokemon that are of decent levels until I get them all transferred over from Sapphire. And even then I'm limited. My best bet personally would be Psychic because I have a couple Girafarig and an Alakazam that are all around level 40.
That works. =) I'll make a note of that. Which one do you want to be which? That is, which one is the level 40ish gym and which is the level 50ish gym?