Let me see here then, if it's Volcanion you have your heart set on as a main deck I'll add my two cents. Before I even start you should know there are a lot of quite difficult match-ups in the Metagame right now, which hold Volcanion back from being top tier. In particular it has a strange relationship with Greninja decks. Obviously this is a difficult-nigh-on-impossible game due to weakness and the potential prize trade, but additionally they form a strange triangle with Garbodor decks. Whenever Garbodor decks are present, Greninja is going to be less so - which is good for Volcanion. But unfortunately that means Garb
is present, which is bad for Volcanion since the deck loses a lot of puff with no access to Steam Up or Flash Fire
Now when Garb is on a downswing, Greninja will rise and now we're back to square one.
The most popular Garbodor decks around right now are;
Scizor-EX & Garb - which Volcanion should handle regardless
Mewtwo and Garb - which becomes very difficult, but not quite an autoloss I don't think?
and DarkTinaGarb - which is maybe a 50/50 draw depending on whether you can stomp Garb before he becomes an issue.
Annnyway, enough catch up on the Metagame, let's talk Volcanion.
4 (or 3) Volcanion - this is the main attacker of the deck and your preferred starter.
3 (or 4) Volcanion-EX - as bulky as it is, it's really only support for it's steam up ability, and a last resort attacker.
2 (or 3) Flareon-EX- this is the direction I usually see the deck go. I don't know if I'm a fan as the baby Volcanion should do the job lategame once they are charged. However, the synergy can't be denied. Volcanion puts energy on Flareon & one other mon, Flareon then uses it's ability to consolidate the energy in one place. You can be hitting big big numbers by turn 2. I think my personal preference would be to rely on the baby Volc to do the job, but it will take some experimentation.
1 Entei (AOR41) - I usually see this included. I am not entirely sure why it's so critical. Perhaps a regular Volc player can enlighten? It does OHKO (assuming Steam Ups) a Regice a lot easier than baby Volc can. It also dumps ammo into the discard for you if you start it. And it benefits from Steam-Up of course. It is most likely added in to deal with the plethora or MegaRay & Rainbow Road decks doing the circuit at the minute. Local-Meta-dependant. I suppose you could even run 2 or 3.
Now you'll note I haven't included Hoopa here, or even Shaymin. The trouble with this deck is, you nearly always want a full five slots on the bench filled. One baby V in active, another on the bench, 2-3 Volc-EX on the bench, add in a Flareon or an Entei and you're already flat out of room. And with no Az / Cassius / Scoop-Up in Standard to lift Hoopa or Shaymin off the bench easily, well now you've hit the second thorn in the side of Volcanion players (the first was the Meta as it stands).
Of course the deck benefits greatly from the speed Hoopa and Shaymin bring to the table. So that is your first big question.
I have seen some neat builds with
Octillery included, which I've been meaning to experiment with. Dive Balls grab both it, and Volcanion-EX thanks to the latter's dual typing. Plus with every Steam-Up, you empty a card from your hand for Octillery to refill - that is a game long benefit for the price of one bench slot. You are going to be running many Float Stone/Switch items/Olympia
anyway for those fat EXs of yours, so it's worth looking into.
The alternate would be to run some weird stadium count of three Scorched Earth & 1 Parallel City/Sky Field, allowing you to clear a few slots from the bench when the Stadium shifts from one to the other. The stray Parallel City would also help in matchups with Rainbow Road or MegaRay.
Speaking of Stadia, Scorched Earth is a no-brainer for fueling baby Volc's Power Heater. The loss of battle compressor from the format means you need to thinking smartly about how exactly you get those energies in the discard in the first place. So
4 Scorched Earth, unless you're up to the shenaigans I mentioned above re allowing for Shaymin/Hoopa, and to control your bench size with Sky Field or Parallel City. You might get away with a lower count, but you certainly need it in the early game. Both to fuel the discard and for the draw.
Lastly on Pokemon, I've seen the occasional
AT Torchic thrown in, and also
Team Magma Camerupt. Neither are worth the deck space imo, but could be fun to play around with on the client. I don't believe they'd be part of a competitive build.
4 Ultra Ball - pretty standard count, will double as a way to get energy to discard. If you're running an Octillery version, you can supplement this with some Dive Balls. If not, you are looking to Heavy Ball which will only fetch Volcanion-EX so that's not great. otoh the oft-forgotten
Repeat Ball could have a place here as a 1-of or 2-of.
4 Trainers Mail / Acro Bike - in most decks I automatically add Trainer's Mail, and forgo Acro Bike altogether. However, since a part of this engine revolves around the discard and dumping energies, I think I would plump for some kind of
2/2 split here. This is one of those things you will need to play around with to figure out the right count for you. Could be as high as 4/4 if you can find the room
4 Vs Seeker - Best card in format right now. Four copies in every single deck. Unless you've some damn good reason not to (like you're playing as Vileplume). No negotiations.
3 (or 4) Max Elixir - This one is negotiable. You are already accelerating energy at a fair rate if things are going well. And you will be tight on room by the time we get to the end. But since the deck has tons and tons of basic energy, and all your Pokémon are basics, plus you've a few tools to recycle it back into a thin deck, well your odds to hit here are massive. You may as well call this four free energy attachments. So many decks you can't justify this card since the energy count is low or the basic count is - here we have perfect conditions but not really the need for it. Still, when you start looking for room in the deck (and you will), this might be the first place to start cutting.
Supporters:
5-6 Sycamore / N in your preferred breakdown. If you choose to run no Shaymin I would be leaning to even higher counts here for early game speed. Maybe even seven between them.
2 Lysandre / 1 Hex Maniac - that's a standard count these days. Also
1 Pokemon Ranger is critical in this deck. Since you play nothing except basics, a sole Jolteon can checkmate you. Plus it can double as a surprise way to allow your Volcanion-EX attack twice in a row if it happens to get stuck in the active.
A 1-count of
Fisherman should be something to at least consider. Perhaps you feel you have enough ways to pull energy around without him, but a card that can be retrieved with Vs Seeker at any time is a powerful get-out clause to charge those steam-ups when you need it. A 1-count of
Olympia for similar reasons - you now have a retrievable and repeat use of a switch you might otherwise not have access to if you choose to include it.
Ninja Boy can be a fantastic secret weapon here (and everywhere tbh). Assuming you can't forgo the Hoopa/Shaymin it's a beautiful card to get out of a dodgy opening hand. Even without those, a baby Volc in active with one Energy on, can become a Flareon-EX with three energy on in one foul swoop. Add a few Steam-Ups and there's not much that can survive it at full force 110+30+30+...
Itemwise there are a few musts.
Float Stone, Fighting Fury Belt, Super Rod need all be in here in some count. 3-3-2 feels about right. One copy of Energy Recycler might sub in for one of those Super Rods if you have generous counts of each Pokemon. FFB doesn't seem to be as critical here for the +10 damage numberswise. But all your mons can do with the +40 HP. For damage numbers, Flareon can do with it - so if your focus is him, then up the FFB count. 110+2 steam ups only kills 170 EX without a belt, but it'll hit 180EX with one on.
Energy Reset seems to have been designed especially for this deck, yet I don't know if it really has a place. If you hit it early game, it's simply no use at all. Energy Pouch the same.
Energy Retrieval is worth running 2-3 copies of depending on your count of Fisherman & Super Rod. I've seen the deck containing Preofessor's Letter, but I don't believe it's worth running - you'll be hitting plenty of energy. It can be useful sure - but there's more times when it's an unnecessary card than there is it being an essential one one. I rather have one more energy card in hand.
Energy itself requires a higher than average count. I'd begin experimenting with a count in the 10 to 12 range, and work up and down from there.
Switch & Escape Rope are the final adds. 2 or 3 between them however you want to split it.
These are very important. As is the Olympia, as are the Float Stones. When playing
against Volcanion, you'll quickly discover it is extremely susceptible to Lysandre. More than usual thanks to the fat retreat costs of the EX and Hoopa. And when the baby is not in the active, suddenly the energy acceleration slows way down, and suddenly it becomes a very easy to topple deck altogether. Lysandre and snipe damage from a Fright Night Yveltal, or a Trevenant Break and it's GG without enough switching methods at your disposal.
So, all that said, this is the first Volcanion Deck I have built right now tonight
This is a version with Octillery in for draw, since I believe the bench space is better utilized this way than filling it with Hoopa and Shaymin. I've added a a single Flareon & a single Entei but my focus is on baby Volc as the main and continued attacker for the duration of the game. I'm sure you can google many many Flareon/Hoopa/Shaymin versions easily.
I'll play around with it, and let you know how I get on over the next few days.