Suggestions or advice? Thanks in advance!

[KitKat987]

Hey there~
Looking to improve a team I have here, thank you in advance for any suggestions or advice! ^^

Klefki (F) @ Leftovers
Ability: Prankster
EVs: 252 HP / 252 SAtk / 4 SDef
Bold Nature
- Spikes
- Draining Kiss
- Metal Sound
- Flash Cannon

Charizard-Mega-Y (M) @ Charizardite Y
Ability: Drought
EVs: 4 HP / 252 SAtk / 252 Spd
Modest Nature
- Dragon Pulse
- Flamethrower
- Air Slash
- Focus Blast

Greninja (M) @ Expert Belt
Ability: Protean
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature
- Ice Beam
- Dark Pulse
- Hydro Pump
- Extrasensory

Breloom (F) @ Toxic Orb
Ability: Poison Heal
EVs: 8 HP / 248 Atk / 252 Spd
Jolly Nature
- Spore
- Substitute
- Seed Bomb
- Sky Uppercut

Gliscor (F) @ Toxic Orb
Ability: Poison Heal
EVs: 252 HP / 184 Def / 72 Spd
Impish Nature
- Earthquake
- Protect
- Substitute
- Toxic

Chansey (F) @ Eviolite
Ability: Natural Cure
EVs: 252 HP / 4 Def / 252 SDef
Calm Nature
- Soft-Boiled
- Protect
- Seismic Toss
- Aromatherapy

 

[PlatinumDude]

Despite its healing side-effect, Draining Kiss is rather weak, which is why it isn't worth bothering. Klefki should squeeze in Foul Play somewhere on its move set to take advantage of high Attack opponents:
-Spikes
-Play Rough
-Foul Play
-Thunder Wave
Nature: Impish
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Prankster

or
-Reflect
-Light Screen
-Spikes
-Foul Play/Play Rough
Nature: Bold/Impish
EVs: 252 HP/252 Def/4 SDef
Item: Light Clay
Ability: Prankster

Air Slash has redundant coverage with Fire Blast; Charizard Y's Drought-boosted Fire Blasts do more damage to Mega Venusaur and Conkeldurr:

252+ SpA Mega Charizard Y Fire Blast vs. 252 HP / 4 SpD Thick Fat Mega Venusaur in Sun: 296-350 (81.3 - 96.1%) -- 56.3% chance to OHKO after Stealth Rock

252+ SpA Mega Charizard Y Air Slash vs. 252 HP / 4 SpD Mega Venusaur: 270-318 (74.1 - 87.3%) -- guaranteed 2HKO

252+ SpA Mega Charizard Y Fire Blast vs. 0 HP / 236 SpD Assault Vest Conkeldurr in Sun: 241-285 (68.6 - 81.1%) -- guaranteed 2HKO

252+ SpA Mega Charizard Y Air Slash vs. 0 HP / 236 SpD Assault Vest Conkeldurr: 218-260 (62.1 - 74%) -- guaranteed 2HKO

For that, I'd replace Air Slash with Solar Beam so that Charizard Y has an easier chance against bulky Water Pokemon like Wash Rotom.

Life Orb > Expert Belt on Greninja; it's frail anyways, and the extra power on non-supereffective hits is appreciated.

Breloom must use Technician as its ability, which powers up Mach Punch and Bullet Seed to acceptable levels. Toxic Orb + Poison Heal abuse is better done by Gliscor:
-Spore
-Bullet Seed
-Mach Punch
-Rock Tomb
Nature: Adamant/Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb/Focus Sash
Ability: Technician

The EV spread of 244 HP/32 Def/232 Spe is preferred for Gliscor; this gives it enough Speed EVs to outspeed Naughty Mega Garchomp and those slower to status them before they respond.

What's the point of Protect on Chansey when it doesn't have Wish or Toxic? The preferred spread is 4 HP/252 Def/252 SDef with a Bold nature for better bulk on both ends:
-Soft-Boiled
-Aromatherapy/Heal Bell/Stealth Rock
-Toxic/Thunder Wave/Stealth Rock
-Seismic Toss
Nature: Bold
EVs: 4 HP/252 Def/252 SDef
Item: Eviolite
Ability: Natural Cure

 

[KitKat987]

Despite its healing side-effect, Draining Kiss is rather weak, which is why it isn't worth bothering. Klefki should squeeze in Foul Play somewhere on its move set to take advantage of high Attack opponents:
-Spikes
-Play Rough
-Foul Play
-Thunder Wave
Nature: Impish
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Prankster

or
-Reflect
-Light Screen
-Spikes
-Foul Play/Play Rough
Nature: Bold/Impish
EVs: 252 HP/252 Def/4 SDef
Item: Light Clay
Ability: Prankster

Air Slash has redundant coverage with Fire Blast; Charizard Y's Drought-boosted Fire Blasts do more damage to Mega Venusaur and Conkeldurr:

252+ SpA Mega Charizard Y Fire Blast vs. 252 HP / 4 SpD Thick Fat Mega Venusaur in Sun: 296-350 (81.3 - 96.1%) -- 56.3% chance to OHKO after Stealth Rock

252+ SpA Mega Charizard Y Air Slash vs. 252 HP / 4 SpD Mega Venusaur: 270-318 (74.1 - 87.3%) -- guaranteed 2HKO

252+ SpA Mega Charizard Y Fire Blast vs. 0 HP / 236 SpD Assault Vest Conkeldurr in Sun: 241-285 (68.6 - 81.1%) -- guaranteed 2HKO

252+ SpA Mega Charizard Y Air Slash vs. 0 HP / 236 SpD Assault Vest Conkeldurr: 218-260 (62.1 - 74%) -- guaranteed 2HKO

For that, I'd replace Air Slash with Solar Beam so that Charizard Y has an easier chance against bulky Water Pokemon like Wash Rotom.

Life Orb > Expert Belt on Greninja; it's frail anyways, and the extra power on non-supereffective hits is appreciated.

Breloom must use Technician as its ability, which powers up Mach Punch and Bullet Seed to acceptable levels. Toxic Orb + Poison Heal abuse is better done by Gliscor:
-Spore
-Bullet Seed
-Mach Punch
-Rock Tomb
Nature: Adamant/Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb/Focus Sash
Ability: Technician

The EV spread of 244 HP/32 Def/232 Spe is preferred for Gliscor; this gives it enough Speed EVs to outspeed Naughty Mega Garchomp and those slower to status them before they respond.

What's the point of Protect on Chansey when it doesn't have Wish or Toxic? The preferred spread is 4 HP/252 Def/252 SDef with a Bold nature for better bulk on both ends:
-Soft-Boiled
-Aromatherapy/Heal Bell/Stealth Rock
-Toxic/Thunder Wave/Stealth Rock
-Seismic Toss
Nature: Bold
EVs: 4 HP/252 Def/252 SDef
Item: Eviolite
Ability: Natural Cure

I'll definitely try it out! Thank you very much again :)