Update 1:
Bug Monotype on Fire Red
So, I picked Charmander as my starter. Ventured out, caught a Caterpie and Weedle. I then released Charmander so I wasn't tempted to use him. I trained my Caterpie and Weedle to eventually evolve into Kakuna, Metapod and then soon after Butterfree, Beedrill.
Entered the Pewter City Gym and challenged the trainer, beat him with ease using Butterfree's Confusion as he failed to pull off any Rock-type moves.
I then went on to face Brock. Butterfree took care of the Geodude in the same way as the trainer, with Confusion. Butterfree was then KO'ed by Onix's Rock Tomb and Beedrill was sent out. It was very close, but Beedrill turned out the victor after somehow surviving 2 turns of Rock Tomb.