i dont remember entirely, but i think they become accessible after corey, so wont help you much.
also, at the patches at the left of corey's gym you can get phanpy
woobats are psychic (strong vs poison) and easy to catch
what i did to beat corey is use a koffing with selfdestruct, which ignites the gas and changes the field, after that, some moves like mudslap are buffed by the new field.
i will explore a bit if there is something accessible to you.
i don't quite remember, is lapis ward available to you at this point, or which wards can you go to ?