So, it seems your Butterfree has Modest as its Nature. As for a set, I have been tinkering all kinds of different ideas for sure to make use of Butterfree. Here's one I just had in mind:
Butterfree @ Wise Glasses
Ability: Compound Eyes
EVs: 4 HP / 252 SpA / 252 Spe
Modest Nature
- Bug Buzz
- Psychic
- Energy Ball
- Quiver Dance
This would be a set mostly to have Butterfree get in with some quick special attacks and sweep them. With this set, Butterfree would cover Grass, Psychic, Dark, Fighting, Poison, Water, Rock, and Ground, with Butterfree having a quadruple weakness to Rock, so that helps.
Here is another set:
Butterfree @ Big Root
Ability: Compound Eyes
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
- Bug Buzz
- Sleep Powder
- Dream Eater
- Quiver Dance
Put the enemy to sleep with Sleep Powder thanks to its accuracy going up due to Compound Eyes, as well as the Big Root giving you more HP from Dream Eater than normal. Bug Buzz for STAB, as well as Quiver Dance to raise Special Attack, Special Defense, and Speed so Butterfree can do more damage with Bug Buzz and Dream Eater, as well as perhaps the pre-emptive strike too.