Few suggestions:
Stataka is only viable when trick room is utilized or defensive. From what I can tell, it's defensive. Use this set only if you want to continue using him.
Stakataka @ Leftovers
Ability: Beast Boost
EVs: 252 HP / 4 Def / 252 SpD
IVs: 0 Spe
Sassy Nature
- Gyro Ball
- Rock Blast
- Stealth Rock
- Protect
A better Pokemon:
Ferrothorn @ Leftovers
Ability: Iron Barbs
EVs: 252 HP / 24 Def / 232 SpD
IVs: 0 Spe
Sassy Nature
- Stealth Rock
- Leech Seed
- Gyro Ball
- Power Whip
Ferrathorn has the bulk, the stats, and the typing to be a good lead against other Pokemon. It's a defensive Pokemon, so be aware of that.
Another popular Pokemon that a lot of people use is:
Landorus-Therian @ Leftovers
Ability: Intimidate
EVs: 252 HP / 112 Def / 144 Spe
Impish Nature
- Stealth Rock
- Earthquake
- Hidden Power Ice
- U-turn
Lando has the good lead as I presume that you want as well as being defensive and having the right coverage. If you'd wanted to go offensive, use this set.
Topapex is with good synergy with lando, so if you'd want to keep Topa, I would if you would use landorous. However, I don't agree with the set. Use this one instead:
Toxapex @ Black Sludge
Ability: Regenerator
EVs: 252 HP / 4 Def / 252 SpD
Calm Nature
- Scald
- Haze
- Recover
- Toxic
Bulky, uses toxic, fills the role of the other toxapex a lot better.
If you go with ferrathorn, use this one set:
Gliscor @ Toxic Orb
Ability: Poison Heal
EVs: 244 HP / 52 Def / 76 SpD / 136 Spe
Jolly Nature
- Earthquake
- Defog
- Roost
- Knock Off
Mewtwo is banned in all forms in ou. One thing in Pokemon is tiers. The top tier are where all the overpowered Pokemon are, such as mewtwo, groudon, kyogre, and rayquaza and etc. is. The tier you listed under are ou, which do have counters against each other. It seems like you want a sweeper, which uses set up moves like dragon dance, swords dance, calm mind, nasty plot, or etc. to boost their stats. Or they have an item, such as choice (put name of item here) and go through someone else's team. Or they could be Pokemon with a natural stat with good support of an ability to make it good (ex:mimikyu with disguise, and shadow sneak) Mewtwo is that type of Pokemon. There are both offensive and defensive sweepers with their own nieche. Offensive Pokemon include:
alakazam
bhlasephalon
charizard x
clefable
exadrill
garchomp
greninja
hawlucha
gayarados
keldeo
kommo-o
kyurem black
landorous
megearna
m lopunny
m mawile
m medicham
mimikyu
m pinsir
swampert
scizor
seperior
tyranitar
volcorona
These aren't the only sets, as you should be creative and make your own sets, such as I made with mine and it does very well.
However, we are working on a simple team, so I will provide you with a offensive and a defensive team sweeper:
Offensive:
Volcarona @ Buginium Z
Ability: Flame Body
EVs: 248 HP / 112 Def / 148 Spe
Timid Nature
- Quiver Dance
- Flamethrower
- Bug Buzz
- Roost
defensive:
Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
- Calm Mind
- Moonblast
- Soft-Boiled
- flamethrower
Now I can see bishop is to pick off threats, put I have a better solution. A much better Pokemon at that is Mega Mawile. Sucker punch, ice punch, fire punch, whatever you need, it has, you just need to strategically know how to use it.
Mawile @ Mawilite
Ability: Intimidate
EVs: 92 HP / 252 Atk / 164 Spe
Adamant Nature
- Swords Dance
- Play Rough
- Sucker Punch
- Knock Off/thunder punch/fire fang/ice punch
Use ice or thunderpuch if you have clefable, but if not use fire fang
I see crawdaunt is another Pokemon to pick off threats. Utilizing orb is very helpful, but with the team that I'm providing for you, it synergies well.
A Pokemon that greatly outclasses craw daunt is greninja. Specifically ash greninja. It's an offensive Pokemon, and is very good at picking off annoying threats such as heatran.
Greninja-Ash @ Choice Specs
Ability: Battle Bond
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Hydro Pump
- Dark Pulse
- Water Shuriken
- Spikes
Defensively, you'd want a Pokemon like m swampers, which is only good in the rain, but well talk about that in the next Pokemon.
Swampert @ Swampertite
Ability: Damp
EVs: 252 Atk / 4 Def / 252 Spe
Adamant Nature
- Waterfall
- Earthquake
- Ice Punch
- hammer arm
we have our starting lead, our defensive Pokemon to take hits, we got sweepers, we got threat pickers. But there's one part of the starter's essential kit that we don't have yet. The support. A key part of Pokemon is the Pokemon that could pivot, heal, get rid of other's sweeping stats. Now there are 3 sets that you can possibly use. Now, these are just suggestions like the rest of the team is, but they probably do their jobs the most effectively in the ou tier.
Wishing umbreon is always helpful to a team in need of support.
Umbreon @ Leftovers
Ability: Synchronize
EVs: 252 HP / 4 Def / 252 SpD
Calm Nature
- Wish
- Protect
- Heal Bell
- Foul Play
or there's also the hazer that gets rid of sweepers easily
Tapu Fini @ Leftovers
Ability: Misty Surge
EVs: 248 HP / 16 Def / 12 SpA / 40 SpD / 192 Spe
Calm Nature
- Defog
- haze
- Scald
- Taunt
And finally the the pivot (use with mega swampert!):
Pelipper @ Damp Rock
Ability: Drizzle
EVs: 248 HP / 36 Def / 224 SpD
Bold Nature
- Scald
- U-turn
- Roost
- Defog
Another pivot sets:
(Usually good with hawlucha with electric seed and unburden and acrobatics)
Tapu Koko @ Electrium Z
Ability: Electric Surge
EVs: 20 HP / 252 SpA / 20 SpD / 216 Spe
Timid Nature
- Thunderbolt
- Defog
- Roost
- U-turn
Another good defensive one:
Tornadus-Therian @ Rocky Helmet
Ability: Regenerator
EVs: 252 HP / 4 Def / 252 Spe
Timid Nature
- Hurricane
- Knock Off
- U-turn
- Defog
A good site to visit for beginners:
https://www.smogon.com
Set credits to:
https://www.smogon.com/dex/sm/formats/ou/
