Best clefable/meganium/swampert/empoleon sets? X/y moves only
Really, Clefable is the best option on your list:
-Calm Mind
-Moonblast
-Moonlight/Wish
-Heal Bell/Flamethrower/Stored Power/Protect
Nature: Bold
EVs: 252 HP/252 Def/4 SAtk
Item: Leftovers
Ability: Unaware/Magic Guard
or
-Wish
-Protect
-Moonblast
-Aromatherapy/Thunder Wave
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Unaware/Magic Guard
or
-Moonblast
-Fire Blast
-Thunder Wave
-Moonlight
Nature: Modest
EVs: 252 HP/4 Def/252 SAtk
Item: Life Orb
Ability: Magic Guard
Why Meganium? It's honestly outclassed by virtually every Grass Pokemon in standard play (Mega Venusaur, Breloom, Ferrothorn, heck even Amoonguss, Chesnaught and Tangrowth are better). Bit of you insist:
-Aromatherapy
-Energy Ball/Petal Blizzard
-Dragon Tail
-Synthesis/Leech Seed
Nature: Calm/Careful
EVs: 252 HP/4 Def/252 SDef
Item: Leftovers
Swampert pretty much needs move tutors to be effective (Stealth Rock, Ice Punch, Superpower). But this is the best it can do with X/Y moves:
-Waterfall
-Earthquake
-Avalanche
-Stone Edge
Nature: Adamant
EVs: 204 HP/252 Atk/52 Spe
Item: Choice Band
Ability: Torrent
or
-Curse
-Earthquake
-Avalanche
-Rest
Nature: Careful
EVs: 252 HP/4 Def/252 SDef
Item: Chesto Berry
Ability: Torrent
While Empoleon's current best set needs tutors as well, it
could still pull of Agility sets:
-Agility
-Hydro Pump/Surf
-Ice Beam/Flash Cannon
-Grass Knot/Flash Cannon
Nature: Modest
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
Ability: Torrent
or
-Substitute
-Agility
-Hydro Pump/Surf
-Ice Beam/Grass Knot
Nature: Modest/Timid
EVs: 12 HP/4 Def/252 SAtk/240 Spe
Item: Petaya Berry
Ability: Torrent
or
-Hydro Pump/Surf
-Flash Cannon
-Ice Beam
-Grass Knot
Nature: Modest
EVs: 140 HP/252 SAtk/116 Spe
Item: Choice Specs
Ability: Torrent