As long as you aren't involved in serious/competetive matches, here are the metas.
Goldfish:
Hwachafish - Hwacha front, close range weapons (flame/carro) side.
Blenderfish - Heavy Carronade Front, close range weapons side.
Lumberfish - Lumberjack front. Side guns at your discretion.
Junker:
No real "meta". The ship is quite versatile and guns are quite variable. But typically
Artemis/Banshee front. Side guns are light gun pairs, like gat-mortar, flame-carro, hades-flak, etc. etc.
Pyramidion:
Metamidion - very common. Gat-Mortar front combination.
Metamidion - variation with Gat-Flak. Not recommended.
Carrotmidion - Pyramidion focused on disables. Flame-carro, carro-carro, or flame-flame.
Galleon:
Hwacha Galleon - bunch of hwachas.
Squid:
Close-range Squid - Flame, carronade, and a gun of your choice.
Spire:
Long-Range - Flak or Lumber, with a long range light guns.
Short-Range - Two gat, mortar, Hwacha/carronade.
Mobula:
No real meta here. Usually either long range or short range.
Excellent list, but I'm making some additions to this that include meta ships used in competitive, or by experienced crews in pub matches
Goldfish:
Hwachafish - Hwacha front, gat or flame side
Blenderfish - Heavy Carronade Front, flame side. This is a ram ship!
Lumberfish - Lumberjack front. flare and flame sides
I always put a flare on the left sides of fishes, it's more efficient to shoot the right side gun.
Junker:
meta junker- Artemis hades left side with front artemis for trifecta, right side gat mortar. Hades and gat are downstairs.
The front deck is the hull engineer (repair the hull from below). The bottom deck is gunner/gungineer.
Pyramidion:
Metamidion - gat mortar
Long range- hades flak/artemis, also merc artemis
Carrotmidion - the "carrot" is carronade artemis. carro flame is very effective, same with gat flame vs pyras
Galleon:
Hwacha Galleon - not nearly as effective as hwatcha carronade (with gat).
meta galleon - hades lumberjack flak left side and hwatcha carronade (or double carro) right.
gunner on lumberjack/hwatcha/carro, buff engi with charged on flak, main engi with lesmok on hades
Squid:
Close-range Squid - carro front flame right.
Bring tar as a squid, you don't need phoenix when your throttle is at neutral.
Double flame squid is the easiest ship if they dont have chem.
Spire:
Flak spire- Merc artemis top with bottom artemis. +variations
Lumber spire- hades mine/flare top with bottom artemis
Short-Range - Hwatcha! Heavy carronades don't really belong on spires (although they are very fun).
For short range, hwatcha gat mortar works quite well (even with AI). Hades artemis/banshee hwatcha is pretty common too.
I am very partial to gat artemis top, artemis hwatcha bottom.
Mobula:
meta mobula is merc with double artemis. Close range guns usually involve flame carro, but there are many variations
mobulas dont need phoenix claw, but they NEED drogue shoot if their balloon breaks (they fall very fast). Hydrogen kerosene drogue chute
Also hades double artemis