You probably won't keep it for too long in the game. Bug types like butterfree are in the beginning of the game for you to fill your team. Its lacking stats will weigh your team down later in the game. So find more powerful pokemon to replace it. But until then, You can give it these moves for early in the game. you should probably find a replacement before going to morty (4th gym) by then, Butterfree will bee really out of place. (pardon the bug pun)
Sleep powder-Good against gym leaders, like whitney, giving you a chance to inflict damage.
STun spore- good to lower enemy speed, then switch to something more powerful.
Confusion-Already have it, butterfree's best offensive stat
Gust-Helps against bugzy while resisting bug attacks