You may also want to consider adding a Dark or a Normal-type to your team as two of your Pokemon are weak to Ghost. Blissey, Chansey and even Diggersby are good choices for Normal-types, while Bisharp, Tyranitar and Greninja make great Dark-type options.
And to add, sets for the Pokemon Boilurn mentioned:
Blissey:
-Aromatherapy/Wish
-Softboiled
-Seismic Toss/Flamethrower
-Toxic/Thunder Wave
Nature: Calm/Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Natural Cure
Chansey:
(same moves as Blissey, but Seismic Toss should be the only offensive option, given Chansey's terrible offenses)
Nature: Bold/Calm
EVs: 252 HP/180 Def/76 SDef
Item: Eviolite
Ability: Natural Cure
Diggersby:
-Return
-Earthquake
-Wild Charge
-U-turn
Nature: Adamant
EVs: 252 Atk/4 SDef/252 Spe
Item: Choice Scarf
Ability: Huge Power
or
-Swords Dance
-Return
-Earthquake
-Quick Attack
Nature: Jolly/Adamant
EVs: 252 Atk/4 SDef/252 Spe
Item: Life Orb/Silk Scarf
Ability: Huge Power
or
-Return
-Earthquake
-Quick Attack
-U-turn/Wild Charge
Nature: Adamant/Jolly
EVs: 252 Atk/4 SDef/252 Spe
Item: Choice Band
Ability: Huge Power
Bisharp:
-Sucker Punch
-Iron Head
-Knock Off
-Substitute/Swords Dance
Nature: Adamant
EVs: 124 HP/252 Atk/132 Spe
Item: Dread Plate/Black Glasses/Life Orb
Ability: Defiant
Tyranitar:
-Stone Edge/Rock Slide
-Crunch
-Pursuit
-Fire Blast/Stealth Rock
Nature: Sassy/Careful
EVs: 252 HP/4 Atk/252 SDef
Item: Assault Vest/Leftovers
Ability: Sand Stream
or
-Stone Edge
-Crunch
-Pursuit
-Earthquake/Ice Punch
Nature: Jolly/Adamant
EVs: 4 HP/252 Atk/252 Spe (Jolly) or 180 HP/252 Atk/76 Spe (Adamant)
Item: Choice Scarf (Jolly)/Choice Band (Adamant)
Ability: Sand Stream
or
-Dragon Dance
-Stone Edge
-Crunch
-Earthquake/Ice Punch
Nature: Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Tyranitarite
Ability: Sand Stream
Greninja:
-Hydro Pump/Surf
-Ice Beam/Dark Pulse
-Extrasensory/Dark Pulse
-U-turn/Hidden Power (Fire)
Nature: Hasty/Timid
EVs: 4 Atk/252 SAtk/252 Spe
Item: Life Orb
Ability: Protean
or
-Spikes
-Hydro Pump/Surf
-Ice Beam
-U-turn/Extrasensory
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Life Orb/Focus Sash
I can re train Goodra for a better EV spread. Would it be possible to keep Flamethrower and Dragon Pulse with the first EV set? My Goodra has a Modest nature.
It looks like I EV trained my future Gengar properly. It's still a Gastly, so I think I'll go for the first move set. I didn't consider Destiny Bond before.
Can you explain a little about Standard Play? Is that official Nintendo play or Pokecommunity? I can give it a Focus Sash when I want to battle in Standard Play.
I'll teach Talonflame Tailwind. To be honest, I was considering it before I taught it Me First.
Nope. Offensive Goodra needs all the power it can get. Defensive sets can play it safe.
Standard play means OU (Overused) play, which is the main tier in simulator battles, like Pokemon Showdown! These tiers are usually organized by other sites such as Smogon.
Also I forgot to mention this about Ferrothorn. It's a defensive Pokemon, and defensive Pokemon shouldn't be holding a Life Orb, as this compromises their good bulk:
-Stealth Rock/Spikes
-Leech Seed
-Gyro Ball/Thunder Wave
-Power Whip/Protect
Nature: Relaxed
EVs: 252 HP/208 Def/48 SDef
Item: Leftovers/Shed Shell
Ability: Iron Barbs
Item clause isn't active in simulator battles. Item clause is when all Pokemon in the team must be holding different items.