Ah, that's actually a pretty good pairing for getting yourself through there. Most of the Pokemon in Ilex are bug type, which are week to fire, and the Weedles and Kakuna are part poison as well, making them vulnerable to psychic.

Of course, both psychic and dark are weak to bug-type attacks as well, but ironically most of the attacks the species in Ilex have at their level qualify as normal or poison type. Just avoid Beedrill and you should be alright.