I haven't chosen an item and I don't think the ability is so important, so I'm just gonna show my moveset, nature, EVs and strategy:
EVs: 6HP / 252 SpAtk / 252 Spe
I always prefer to deal lots of damage. That's why it's modest and has energy ball instead of giga drain.
Sludge bomb is STAB
Sleep powder in case you need it
In case you don't know what that is I'm gonna explain it to you:
Example: Grass Type resists energy ball but weak against sludge bomb, then it's not a threat,
but the only types that resist (or are immune to) energy ball and sludge bomb are poison and steel, that's what I worry about, so to cover that resistance I will use extrasensory to his other poison types super effectively, but not against steel types so it's our only problem. I was thinking about Hidden Power Ground to just kill those resistances but it doesn't have effect or a good power so I preferred extrasensory.
What do you think?