I have a couple of sets for this cheeky little monkey: one is a full on Life Orb sweeper set, the other one a stally one. Here goes!
Sweeper set:
Grookey @ Life Orb
Ability: Grassy Surge
Level: 5
Shiny: Yes
EVs: 37 HP / 236 Atk / 235 Spe
Jolly Nature
- Swords Dance
- Grassy Glide
- Knock Off / Focus Energy
- Drain Punch
The EVs let Grookey live a couple more hits thanks to Life Orb and/or otherwise. Swords Dance to set up if you really need to, but not always, as this Grookey's still strong. Grassy Glide is strong Physical STAB, as well as being Terrain boostes priority: this is what makes Grookey so good. Knock Off is well, Knock Off, and Focus Energy gives higher Critical Hit chances, which are really underrated; that being said, I always go for Knock Off lol. Drain Punch is strong coverage, and healing is great.
~~~~~~~~~~
This next set is the stally one. This one is still very good, so fun to use :)
Grookey @ Leftovers / Berry Juice
Ability: Grassy Surge
Level: 5
Shiny: Yes
EVs: 236 HP / 36 Atk / 235 Spe
Jolly Nature
- Grassy Glide
- Leech Seed
- Protect
- Drain Punch / Fake Out
Grassy Glide is for, as I said earlier, Physical, Terrain boosted, Priority STAB. Leech Seed saps health each turn, which is great, and Protect lets you live a hit to heal more, as well as Grassy Terrain/Leftovers healing too. Grookey's not gonna die lol. Drain Punch is for good coverage as well as healing, and Fake out flinches the opponent. I would go with Drain Punch, however, as Fake Out is usually healed most of the way with Grassy Terrain, and leftovers should the opponent have it. Just me though, do whatever you want ;). The Berry Juice is for healing all the way should your opponent manage to whittle you down.
Let me know if this helps, I hope it does!