How do you beat bug type Pokemon on gold?
one of bug's main weakness is fire. hit it with strong fire type move example: flame thrower, blast burn.
If you are talking about Jasmine you just need a fighting type pokemon or a pokemon that knows a fighting type move. Or a fire pokemon or a pokemon that have fire type move is fine. And if you are talking about Sabrina she is a psychic type master so you will need a bug/ghost/dark type pokemon or a pokemon that have the move type.