Gholdengo

Decklist

• This is just the standard list
• Mawile is the best Cornerstone counter, but Lopunny could still be worth playing
• Lana's Aid helps against Jellicent but that's basically the only use for it, so you could cut it. I think Lana's Aid provides a decent edge against mediocre Jellicent players. Could also cut a Poffin.
• Vitality Band and Premium Power Pro are very strong and give you some agency. Makes Solrock more powerful, which is good when the game is either going off script (such as if you prize Genesect and can't find Gholdengo), or when you need a single-prize board.
• Although four Nest Ball is good, I think having the second Artazon over the fourth one is better because you sometimes want to bump Stadiums such as Jamming or Lively.
• Four Dengo is not necessary.
• I am fairly sure Prime Catcher is the best Ace Spec but I could be wrong
• 50 HP Gimmighoul is not worth it! It is a huge liability in so many situations, even though Call for Family is sometimes good. I did include some stuff about 50 HP Gimmi in the matchup notes because most people play it.
• I think Super Rod is better than Stretcher because putting Fightings back in the deck helps against Iono, and because sometimes you want to draw a lot and use Super Rod to not deck out. Also, three is better than one, and Gholdengo has plenty of search and draw to mitigate Super Rod's downside.
• Team Rocket's Watchtower seems like a really good counter to Charizard/Noctowl in theory (along with Secret Box), but it doesn't help all that much in reality. It maybe adds a few percentage points in that matchup, but it's still unfavorable, so I don't think it's worth it. Also, playing Secret Box sucks. I often miss the option to Arven for Prime Catcher or Prime+Turo in the same turn.

To try: Lopunny, maybe TM: Evo, Munkidori version

Gameplay

• If you're going to use Superior Energy Retrieval, pay attention to how much Energy is in your discard. Sometimes you need to discard Energy with Vessel/Retrieval to get maximum value/"free" Energy from each Superior.
• Sequence based on what you need for the turn. If you don't need to draw into any more Energy for the KO, use Fighting Gong and Vessel to get the Energy out, then draw. If you have Fighting Gong but already have Solrock, Lunatone, and Fighting Energy, usually draw first. If you need to fill your board, draw before using Nest Ball, etc.
• Active Coin Bonus/Fez first, then Lunar Cycle or benched Coin Bonus. If there's a chance you won't want to use Lunar Cycle, benched Coin Bonus first. If there's a chance you'll make the benched one active for extra card, Lunar Cycle first. Arven is usually last in any sequence.
• Keeping extra Earthen Vessel/Gong around can help against Iono at any point as long as there's Fighting Energy in the deck.
• If you have an extra attachment for the turn, consider if you could close out the game with Mawile. Sometimes it's easier to get lethal off Iono via Mawile than Gholdengo
• Always look for opportunities to use Solrock or single-prize board to throw off your opponent's prize trade.
• Prioritize discarding Metal Energy off Make it Rain because Fighting is more useful to have around. You'll need to use Superior anytime you need Metal anyway. With Vessel, search out enough Fightings for the immediate future, then prioritize searching out Metals to make Fighting Gong still useful.
• Preemptively using Arven for Prime Catcher can enable powerful Prime+Turo plays later.

Matchups

Dragapult / Dusknoir - Slightly Favorable

• When multiple Energy are prized, be careful with managing Energy so that you can always one-shot Dragapult.
• Sometimes pre-loading Genesect with an Energy can be good to play around the stall. This is very situational.
• Putting the 50 HP Gimmighoul down (if you play it) is ok if you can immediately evolve it before it gets sniped. Otherwise, try to avoid putting it down at all. If no Gimmighoul are prized, you can sometimes play the game without ever benching the 50 HP one.
• Even though Genesect is a liability, it's still good to slam into play as soon as possible.
• If you get the chance to Turo the Genesect later, even if it doesn't have any damage, it still avoids the trap or Ursaluna lose-cons

Gardevoir / Jellicent - Unfavorable

You need to get an aggressive start, try and get as much of a prize lead as possible. This will make it difficult for them to pivot into a prize trade and force them to rely on Frillish and Devo.

• Ideal board depends on the situation, but usually it's 3 Dengo, LunaRock, and an open spot for Fez, Genesect, or Mawile. Genesect always gets used, but sometimes you want to Turo it up. Three Dengo is good because it's easier for them to Devo the fewer Dengo you have, which is very relevant.
• Otherwise, using Turo on damaged Gholdengo, LunaRock, or Mawile can be good to throw off their prize trade.
• Watch out for their opportunities to pivot into an aggressive prize trade. Sometimes you need to Turo or avoid benching single-prizers because after they kill your first Solrock, they only need to pick off one more single-prize Pokemon to then go 2-2 to close out the game.
• Try to play Picnic Basket on any turn you can get value from it and aren't Item locked. It's very strong but difficult to use.
• Mawile can be very strong if they are trying to spam Frillish, just watch out for Mew Counter Catcher (and try to Turo the Mawile if they hit you with that).
• Don't hit the Frillish for less than a KO for no reason. It's ok to punch it if you're applying relevant pressure, but if they have two Munkidori with Dark, it's usually best to not hit into it.
• Try to one-shot the Frillish whenever possible. If they have Charm, use Gholdengo with three Energy, otherwise use Solrock with Vitality Band
• If you decide to KO their Gardevoir, make sure you have enough resources left to deal with the Frillish. Lana's Aid plus Mawile can help with this.

Charizard / Secret Box - Favorable

• KO Pidgeot so they cannot find Briar
• Solrock is great in the early-game, but try to take two-prize KO's with Gholdengo whenever possible, pressuring their Charizard or KO'ing their Pidgeot.
• Sometimes delay benching Genesect so they cannot get a two-prize KO. Sometimes stagger Gholdengos so you can play with a single-prize board, but this is situational because they can Iono you.
• Premium Power Pro and Vitality Band can be good to allow Solrock to trade into Chi Yu or KO Pidgeotto/Charmeleon.
• Apply fast pressure to their board, using Prime Catcher if necessary. The most consistent way to win is by getting far ahead at the beginning. If they only have one Pidgey, KO that. KO'ing Tatsugiri and Charmander can also be good.
• Turo can very situationally be useful to make a single-prize board, otherwise it is basically useless. Gust cards are extremely important and can be used aggressively (but not discarded!).

Charizard / Noctowl - Unfavorable

The winning prize trade is pretty idealistic. You need the first KO (usually with Solrock). If they take one prize, get a two-prize KO in response. They take two back. Take two more prizes, going to one, profit. This successfully plays around Dusknoir and Briar, but it's hard to pull off. In other words: 1-2-2-1 prize map.

• If that prize map does not line up, you can make use of multiple Solrock to KO important Pokemon like Hoothoot or Duskull while trying to keep the two-prize Pokemon safe.
• Another cheeky way to win is by super aggressively targeting the Charmander lines and trying to run them out of Charizard. If you are going for that, try to avoid feeding Fez or Genesect to Terapagos by using Turo or not putting them down. If the anti-Charizard line isn't feasible, KO'ing Hoothoot or Duskull are generally good options.
• Pay attention to both players' prize counts and Charizard's breakpoints.
• Utilize Gholdengo's HP in the early-game, as they cannot one-shot it (especially if you KO Duskull). This is especially strong in the rare scenario you have only Gholdengo in play so they cannot KO anything.
• If for some reason they punch Gholdengo for less than a KO and put it into Dusknoir range, use Turo to heal it. Keeping one Turo around is generally good to stop plays like that, or for the above-mentioned plays.

Absol - Favorable

• If they go only Cornerstone board, do not attack. Solrock never makes any real progress and it disables Mawile's second attack. If they only have single-prize targets, ignore them because you don't want to proc Counter Catcher. If this scenario happens, just load up Mawile and sweep them with its second attack.
• If they have two- or three-prize targets on their board, play normally and KO them with Gholdengo. If they start putting Energy on Cornerstone, then start powering up Mawile.
• Save Turos for if they try to smack Mawile (or for retreat lock). Use Picnic Basket on Mawile if you are about to start attacking with it. Picnic Basket can also be good on Gholdengo to deny prizes. Saving Prime Catcher for retreat lock is also good so that you can use Turos elsewhere such as on Mawile.
• Save Super Rod because you might need to dig for cards like Artazon/Turo and not deck out later.
• Save Artazon for when you need to one-shot through Charm+Lively Stadium!
• Ideal board is two Gholdengo, Solrock, Lunatone, Mawile, and Genesect if you need it (which you usually do).
• Try to not give too many prizes up to Cornerstone or else they can just win a normal prize trade.

Grimmsnarl - Favorable

• Leave backup Gimmighouls unevolved for awhile so they don't take Froslass damage.
• Genesect on board ensures you can always get Gholdengo even if you get Iono'd.
• Save Turos for retreat lock. Saving Prime is good too, but using it for fast pressure is fine as well.
• Ideal board is Gholdengo, two Gimmighoul, Solrock, Lunatone, Genesect
• Premium Power Pro is often useful for applying pressure with Solrock
• One-shot their Grimmsnarl whenever possible, otherwise target Froslass and Snorunt!

Mirror - Even

• Do not feed them Gimmighoul unnecessarily. Sometimes it's better to wait a turn before putting Gimmighoul down because Solrock cannot KO it. When you do put Gimmighoul down, you definitely want to put down at least two. Usually don't put down just one, better to wait. In the same way, don't put down unnecessary Gimmighoul when you already have Gholdengo established.
• Pay attention to their prize map and make it difficult for them depending on the prize count, utilizing single prize board, no Gimmie board, or Turo depending on the situation.
• Premium Power + Vitality is obviously broken for getting a Solrock KO on a turn you shouldn't be able to do anything, but don't use it if you have another available play because you might need it later.
• Gusts and Turo are premium resources

Personal thoughts

Gholdengo is extremely strong. Its matchups are alright even though it does have some weaknesses. I would put Gholdengo in my top 3 plays. I would personally rather play Gardevoir or Charizard/Noctowl due to slightly superior matchup spreads as well as more agency. Gholdengo has basically no skill expression, so you're more at the mercy of luck than with other decks. All that said, it is an insane deck and definitely worth playing.