I see you've got your stuff together. Fully-competitive Pokémon, competitive items, fricking Aegislash... it's good. However, one thing that you lack is balance. You have all physical attackers. You have very little types coverage attack-wise. I'm gonna give you a little formula that I use for building three-Pokémon teams, as well as Battle Maison advice as well.
My Formula
When I build a Battle Maison/Battle Spot team, I always choose one physical sweeper, one special sweeper, and one bulky Pokémon. My first team consisted of Blaziken, Gardevoir, and Mega Salamence.
Blaziken@ Shell Bell
Ability: Speed Boost
EVs: 252 Atk / 252 Spe / 4 HP
Jolly Nature
High Jump Kick / Protect / Earthquake / Flare Blitz
Salamence@ Salamencite
Ability: Intimidate > Aerialate
EVs: 252 HP / 252 Atk / 4 Def
Adamant Nature
Dragon Claw / Dragon Dance / Roost / Return
Gardevoir@ Choice Scarf
Ability: Synchronize
EVs: 252 SpA / 252 Spe / 4 SDef
Moonblast / Trick / Psyshock / Shadow Ball
This team bulldozed Single Battles and got to a streak of 27 in Super Single Battles. All because of good timing, training, and planning. I carefully researched the best and most up-to-date competitive movesets (I bring this up because your Greninja is so X and Y). You need to make sure that your Pokés are balanced type-wise, attack-wise, and stat-wise. Good Pokémon for this formula are Landorus, Mega Lopunny, Garchomp, and Rotom-Wash/Heat.
Another one of my formulas (it hasn't been tested yet, so be warned) is one physical tank, one special tank, and one mixed sweeper. Your team may fit better into this category. Good Pokés for this formula are Mega Sableye, Slowbro, Tangrowth, Tyranitar, Hippowdon, etc.
Tips
1 - Make use of your resources! The Move Tutors are right nearby, and the shop has a plethora of useful items (Toxic Orb for Gliscor, Choice Band for Scizor, etc.) which can usually be afforded after one round of Single Battles.
2 - Look around the web for other, more experienced battlers; sites like that include here, Serebii, and Smogon. Most people will be more than willing to help you.
3 - Experiment. If one Pokémo ndoesn't work, try another one. Keep trying until you find the right one. Research. Trade. Breed. The possibilities are endless.
Your Team
I'm just going to make small improvements to your team's Pokémon that should help improve them. Changes will be in bold.
Greninja@ Life Orb
Ability: Protean
EVs: 252 Spe / 220 SpA / 36 Atk
Naïve Nature
- Ice Beam
- Hydro Pump
- Gunk Shot
- U-Turn
EVs are slightly redistributed, and the nature is switched to Naïve to give Greninja more power behind his physical attacks. Gunk Shot is all the rage now, giving your team an invaluable anti-Fairy Pokémon. U-Turn is staple for Greninja, and when paired with his high Speed, he should be able to escape any scary threats. Greninja also
Salamence@ Salamencite
Ability: Intimidate > Aerialate
EVs: 252 Atk / 252 Spe / 4 Def
Ability: Jolly
- Return
- Dragon Claw
- Dragon Dance
- Roost/Substitute
The only changes to make here is the substitution of Earthquake for either Substitute or Roost. Subs give protection and opportunities to set up DDance, but Roost lets you last longer.
Aegislash@ Weakness Policy
Ability: Stance Change
EVs: 252 Atk / 252 HP / 4 Spe
Adamant Nature
- Sacred Sword
- Swords Dance
- King's Shield
- Shadow Sneak
What the heck does "Maxed but distributed evenly" mean? Not trying to be rude, but that makes very little sense. I gave it the best EVs for the set you are running. Calm is fine for the nature, but Adamant helps kill things a little better.
So there you have it, my analysis of Battle Maison Singles. Just a few parting notes:
1) Remember, while your opponents are NPCs, they are smarter than average. Don't let them catch you off guard.
2) Luck is not always on your side. I have been screwed so many times by missing with High Jump Kick, once it was twice in a row. Be wary when using moveswith questionable accuracy.
3) Choose wisely. Weigh the options carefully: Who fits my team better, this Pokémon or this one? Is it best to nab another boost, or should I play it safe and just go for the KO? Do I have a backup in case this check goes down? Pokémon battling is all about choices, and it's up to you to make the choice you feel is best.
