My OU Team! :D

[Lamp]

Hi there! Just got back to the PKMN Competitive Battling Scene! :D
I wasn't Really Sure how good this Team is but can you See and
Tell me if it's Good or Not. 3...2...1...Go! btw

My Team:

Bread (Breloom) @ Fighting Gem

Trait: Technician
EVs: 252 Spd / 252 Atk / 4 HP
Jolly Nature
- Bullet Seed
- Mach Punch
- Stone Edge
- Swords Dance

Eggs (Blissey) @ Leftovers

Trait: Natural Cure
EVs: 252 Def / 252 SDef / 4 HP
Calm Nature
-Aromatherapy
-Seismic Toss
-Soft Boiled
-Toxic

Milk (Keldeo-Resolute) @ Life Orb

Trait: Justified
EVs: 252 Spd / 252 SAtk / 4 SDef
Timid Nature
- Secret Sword
- Hydro Pump
- Hidden Power [Ice]
- Calm Mind

4 (Donphan) @ Leftovers

Trait: Sturdy
EVs: 252 Def / 252 HP / 4 Atk
Impish Nature
- Earthquake
- Rapid Spin
- Stealth Rock
- Ice Shard

5 (Kyurem-Black) @ Choice Scarf

Trait: Teravolt
EVs: 252 Spd / 252 Atk / 4 SAtk
Naive Nature
- Outrage
- Fusion Bolt
- Ice Beam
- Earth Power

SSBBZ (Lucario) @ Life Orb

Trait: Inner Focus
EVs: 252 Spd / 252 Atk / 4 Hp
Hasty Nature
- ExtremeSpeed
- Bullet Punch
- Close Combat
- Swords Dance

 

[PlatinumDude]

It may seem tempting to give Breloom Coba Berry to weaken Flying moves, but they're not that common outside of Hurricane and Brave Bird, and those still hurt. It's also tempting to give Techniloom Rock Tomb, but it's still weak and Stone Edge outdamages it:
-Swords Dance
-Bullet Seed
-Mach Punch
-Spore (it eases setup and supports the team at once)
Nature: Adamant/Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Focus Sash/Fighting Gem
Ability: Technician

Cloyster's terrible defensive typing holds it back from using a support set. It's better off using an all-out attacking Shell Smash set:
-Shell Smash
-Icicle Spear
-Rock Blast
-Razor Shell/Ice Shard/Hydro Pump
Nature: Jolly/Naive
EVs: 4 HP/252 Atk/252 Spe
Item: White Herb/Focus Sash
Ability: Skill Link

If you want to use a hazard/Rapid Spin supporter, go for Donphan instead:
-Earthquake
-Rapid Spin
-Stealth Rock
-Ice Shard
Nature: Impish
EVs: 252 HP/4 Atk/252 Def
Item: Leftovers
Ability: Sturdy

HP Ghost/Ice are the better options over HP Electric on Keldeo. Not only does HP Ghost still deal with Jellicent, it also allows Keldeo to deal with other Ghosts/Psychics, like Celebi. HP Ice, on the other hand, still deals with Celebi, but also hits Dragons hard.

Cresselia performs best at Sun teams. Despite Espeon's fraility, it's the superior option for a screening supporter outside of Sun:
-Reflect
-Light Screen
-Psychic/Psyshock
-Hidden Power (Fire)
Nature: Timid
EVs: 252 HP/4 Def/252 Spe
Item: Light Clay
Ability: Magic Bounce

Zen Headbutt is a subpar option on Black Kyurem; really, the only thing it hits are Fighting Pokemon. Outrage hits them hard enough already:
-Outrage
-Dragon Claw
-Fusion Bolt
-Ice Beam/Earth Power
Nature: Hasty/Lonely
EVs: 252 Atk/4 SAtk/252 Spe
Item: Choice Scarf

While Lucario's Speed isn't the best, priority abuse isn't one of its main specialties, given how weak priority moves are in general, outside of ExtremeSpeed and Sucker Punch. You're wasting away the fact that it has Swords Dance and Nasty Plot to amp up its power:
-Swords Dance
-Close Combat
-ExtremeSpeed
-Crunch/Ice Punch/Bullet Punch
Nature: Adamant/Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Life Orb

or
-Nasty Plot
-Aura Sphere
-Shadow Ball/Dark Pulse
-Vacuum Wave/Hidden Power (Ice)
Nature: Modest/Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Life Orb

Something else to consider on the team is Blissey, who can absorb special blows easily and support the team at once:
-Stealth Rock/Aromatherapy
-Seismic Toss/Flamethrower
-Softboiled
-Toxic
Nature: Calm
EVs: 4 HP/252 Def/252 SDef
Item: Leftovers
Ability: Natural Cure

or
-Wish
-Protect/Softboiled
-Seismic Toss/Flamethrower
-Toxic
Nature: Calm
EVs: 4 HP/252 Def/252 SDef
Item: Leftovers
Ability: Natural Cure

 

[Lamp]

hmmm.... I see i think i know what to do...

 

[Boilurn]

Well, as for how the team looks now, I see errors in terms of defensive synergy. None of your team resist Psychic, Flying or Fighting-type moves, so Pokemon such as Reuniclus and Staraptor may be able to sweep your team. A Ghost-type Pokemon makes a solid team-mate to replace Lucario or Breloom, as not only they have an immunity to Fighting and can eliminate Psychic-types with their STAB moves, but they can also switch in to prevent Pokemon that attempt to remove Stealth Rock. Jellicent is the most common Ghost-type in the tier that isn't weak to Psychic, although you could also try Sableye and Rotom, as they resist Psychic and Flying-type moves respectively as well as Fighting, even though they aren't as common.

Offensively, I recommend having at least one Fire-type move, such as Hidden Power Fire, on one of your Pokemon, as these moves can quickly eliminate Scizor, Forretress and Ferrothorn from the match.

I hope my advice helps as well as PlatinumDude's, Good luck in the competitive battling world.