I'm looking for some suggestions for improving my team for the Battle Maison/Institute, as I need to farm some BP to get evolutionary items. I had no issues with the Elite 4 (outleveled them by about 5-9 levels to be fair), but being limited to 3 out of 6 Pokemon, no items, and getting level-matched, is making my initial attempts at the grind pretty slow. My best was probably only to round 11 sadly. My team isn't properly EV trained so I know that's an issue I can fix, just not sure which stats to go for on each. Any insight would be super appreciated. Not really looking to play competitively but getting a 50 win streak which supposedly upgrades your trainer card would be an awesome goal to shoot for eventually.

My team:
Mawile with Intimidate holding Mawilite (normally a beast but gets shut down by fire moves and earthquake)
Iron Head, Iron Defense, Play Rough, and ??? (I had attract, changed to false swipe when filling out pokedex)

Aurorus with Refrigerate holding Icicle Plate
Thunder Wave, Light Screen, Ice Beam, Rock Slide

Golduck with Damp, holding Splash Plate
Confusion, Surf, Soak, Calm Mind

Vivilion with Shield Dust holding Insect Plate
Aerial Ace, Bug Buzz, Aromatherapy, Stun Spore

Pyroar with Unnerve holding Fire Plate
Noble Roar, Strength, Fire Fang, Work Up

Chesnaught with Overgrow holding Meadow Plate
Needle Arm, Spiky Shield, Power-Up Punch, Bulk Up

There are many ways to EV train a Pokemon (largely dependent on what role you want it to play in your party), but you can usually EV train a Pokemon's best attributes and have it turn out semi-decent. Good IV (Individual Values) help as well, but those aren't required to burn through the Battle Maison.

I'm not in a position to give you a proper moveset for the Pokes (sorry), but you should always try to maximize your coverage. For example, Chestnaught has acceptable Attack, so try to give it good physical attacks to take advantage of its grass/fighting typing. If you're thinking of having an offensive Chestnaught, you'd benefit from having some Attack (y'know, to kill shit) and Defense (so you have a chance of surviving a flying/fire attack).

Also, it helps to have some variety in the Pokemon that you use for the challenges. As things are right now, Fire and Ground types tear your Pokemon apart, so try to mix things up a lil' bit.

Get rid of Iron Defense on Mawile, it's already a physical wall that can now hit and potentially set up sweeps with it's mega. I'd either go with Toxic/Brick Break or Power-Up Punch/Substitute or Taunt/Stone Edge. If you have leftovers I'd put it on otherwise I'd Choice Scarf it if you can manage to get one.

Take the Icicle Plate off Aurorus, maybe run Life Orb or a Sitrus Berry. You should be running Stone Edge not Rock Slide because it's special based not physical. TWave is pointless because it's going to get outsped no matter what and you should only take out Aurorus when you know you can take the next hit and instantly set up Light Screen (You could get rid of Light Screen if you want to be more offensive and use Rock Polish instead). Replace TWave with Thunderbolt only if you run the Light Wave set, if you use Rock Polish use Freeze Dry to slap water types for a surprise.

I'll come back to this thread and help some more but kind of busy atm.

I can get through the Battle Maison no problem but I'm pretty bad against other people so this might be bad advice.

What natures are your Pokemon? They will increase one stat and decrease another by 10%. When you look at your Pokemon's summary a red colored stat means it's boosted, blue means it's reduced.

An unreliable but fast and easy way to decide which EVs to train is to look at the stats. Train the higher Attack stat. Give slow Pokemon more HP, make faster Pokemon even faster.

My Mega Mawile has Swords Dance instead of Iron Defense and Sucker Punch, which is a priority move (moves first regardless of speed) that only works if the other Pokemon attacks. If I know the other Pokemon can't hurt it, I use Sword Dance to buff its Attack stat then use a move that's appropriate. With Sucker Punch you have to predict correctly otherwise you're giving your opponent a free turn. It's my favorite move on the set. A lot of fast Pokemon are super frail and Mega Mawile's Attack is so high, it will just kill most things in one hit even if it's not effective, especially after a Swords Dance or two. I EV trained for Attack and HP with an Adamant Nature.

I'm a little disappointed in Aurorus. It is pretty bulky but it has terrible typing. Everything from an Earthquake to a Mach Punch will kill it even if it's trained in HP. Stone Edge is a Physical Attack, too. The best Special Rock it gets is Ancient Power. It's pretty weak. But it's the same power as Thunderbolt after type bonus. Train for Special Attack and HP.

Put Psychic or Psyshock instead of Confusion on your Golduck. The 10% chance to confuse the target isn't worth it. Special Attack and Speed or HP.

You should get rid of that Aerial Ace on Vivillon. You won't make a dent in anything. It's a Physical Attack and Vivillon can't deal with that.

Pyroar is a Special Attacker. You should change Strength and Fire Fang to Hyper Voice and Flamethrower/Fire Blast/Overheat. EVs in Speed and Special Attack.

Chesnaught isn't fast enough to make good use of Needle Arm's flinching effect. Seed Bomb or Wood Hammer would be better. I don't think you need Bulk Up and Power-Up Punch on one set. It learns Sword Dance which is pretty much the best move to throw on anything. Spiky Shield doesn't do you much good if you don't poison or Leech Seed your target first. Otherwise you're just biding time. You have several options here. Either you go all offensive with Wood Hammer/Seed Bomb, Hammer Arm/Low Sweep, Earthquake/Stone Edge, Swords Dance/Bulk Up. Or you go a bit more passive with Leech Seed and/or Toxic, Spiky Shield, some attacks, with Leftovers. EVs in HP and Attack on both sets.

If I had to pick a team of three out of those six, I would go with Mawile, Aurorus and Chesnaught. But they are all bulky and slow, so maybe Pyroar instead of Aurorus. Try to not use the plates. Boosting just one attack type might end up being a waste of an item slot. Bulky Pokemon love those Leftovers. Life Orb is good but you would have to spend some of those BPs you are trying to save up for those evo items. Expert Belt, Wise Glasses, Quick Claw, Shell Bell, Big Root are all items you should already have.

Thanks for the advice, everyone. I started looking into how IVs and breeding work since I have access to a Ditto safari so I might mess around with that to get a better 3rd option to go with Mawile and Chesnaught. But you've certainly given me a lot to think about.

Well I fell down the rabbit hole of breeding for IVs. I caught some safari Dittos and a Gooey Sliggoo this morning, and by the afternoon I had a Bold Gooey 31/x/31/31/31/31 Goomy. Trying out EVs in HP and Special attack. I have to say that was incredibly fun and satisfying, and also I can't imagine trying to do that without the friend safari and destiny knot. I know I'm going to teach it Dragon Pulse and Sludge Bomb, I'm not sure about the other 2 moves though. Possibilities are Flamethrower, Thunderbolt, Rest, Protect. Also I guess I'll give it leftovers. Any advice on the 2 moves?

@alanm26v5: If Goodra is going to be your third guy with Mawile and Chesnaught then I wouldn't put Sludge Bomb on it. That might save it from a Fairy but you shouldn't face one with Goodra anyway when you have Mawile. Rest would be better on a Hydration Goodra on a Rain Dance themed party. Just go all attacks on it if your main goal is to beat the Battle Maison. You can check for type coverage here. Chesnaught and Mawile are both weak to fire so maybe put Muddy Water on Goodra. I would go with Dragon Pulse, Muddy Water, Flame Thrower, Thunderbolt.

You might've already heard by now, but if you need help on deciding what stats to EV train, serebii.net usually has charts outlining what the maximum value a stat can have: one for a beneficial nature, one for the neutral natures, and one for natures that hinder the best stats for those Pokes. Might save you some time.

Can you get EVs from battle maison?

EV training isn't necessary but it can help. First off I found double battles easier (you can use 4 pokemon), especially when using Mega Mawile which you can pair up with a trick room user such as Reuniclus. My mawile (intimidate ability) has sword dance, sucker punch, iron head and play rough. My Reuniclus (with magic guard ability and life orb item) has shadow ball, trick room, focus blast and psychic. In the first turn I mega evolve and sword dance, while my Reuniclus uses trick room. This will let you always hit first and hard after one turn of setup. Both mons should be able to take a hit during the first turn. I made it to the 60s using this core strategy and only lost because my other two didn't pull their weight.