As of right now, breloom is one of those pokemon like bisharp can't really do well outside of a 252 attack and 252 speed. As far as sets goes, a recent EU Regional winner Baz Anderson used a breloom whose moveset largely consist of bullet seed, mach punch, protect, and spore. I think the main different between breloom sets is if whether they want to run adamant or jolly.
Edit: Focus Sash is generally the best items just to spread spores
Breloom
Nature: Jolly/Adamant
Item: Focus Sash
Ability: Technician
Evs: 4 HP / 252 Atk / 252 Spd
Moveset:
Bullet Seed
Mach Punch
Spore
Protect
Edit: Focus Sash is generally the best items just to spread spores
Breloom
Nature: Jolly/Adamant
Item: Focus Sash
Ability: Technician
Evs: 4 HP / 252 Atk / 252 Spd
Moveset:
Bullet Seed
Mach Punch
Spore
Protect