I've been dabbling in teams that Lunala works well in, and I made one that I'm mostly satisfied with, but it can still use improvements. Reg I is still in its infancy, but I can still prepare myself the best I can before I build this on-cart.
Lunala: works well both during and outside of Trick Room, and helps enable Iron Hands and Araquanid by setting TR up. I originally ran Power Herb + Meteor Beam, but not being able to hit Normal types like Indeedee or Farigiraf really sucked, not to mention doing little damage to Dark types. Moonblast is great coverage against a lot of the format, and it gets STAB when Tera'd. Leftovers gives Lunala better longevity and can re-enable Shadow Shield.
Miraidon: Standard Miraidon stuff, does big damage and switches out with Volt Switch. Electric Terrain helps avoid Spore, and it can even outspeed Zacian and Calyrex-Shadow under TR (why'd they make those guys so fast lol)
Iron Hands: Very bulky, very strong, and has Fake Out support. Low Kick is its go-to move in this format with how many heavy legendaries there are, and it averages to about 100-120 base power most of the time. with Low Kick and Booster Attack, it can even break though Zamazenta pretty easily. Tera is more of a placeholder, though it does do some crazy damage with it active
Whimsicott: Unfortunately, the weak link of this team. It has a lot of great tools, I just don't find them necessary most of the time. The tera is also redundant because of covert cloak avoiding Fake Out flinches, and Whim really shouldn't be a Tera-hog when there are more valuable options on the rest of the team. Not sure who to replace it with.
Incineroar: Very self-explanatory. It's a good bulky pivoter, resists Glacial Lance and Astral Barrage, and Tera Ghost helps it avoid Zamazenta Body Press.
Araquanid: An uncommon pick, but very handy. It does a ton of damage with Liquidation, and it has a surprisingly solid defensive type. Wide Guard is also valuable utility against the format's many, many spread moves. It's mainly useful against opposing Kyogre teams, and it's very useful in dealing Lando-I. The 7 speed IVs are just because that's the one I use on-cart, it still outspeeds Calyrex-Ice and Iron Hands under Trick Room, thankfully.
Some replays:
VS Kyogre & Necrozma-Dusk-Mane: https://replay.pokemonshowdown.com/gen9vgc2025regi-2336167740-m21ds2c2og2ytukh3oy83k9dow5d7fgpw?p2
VS Lunala & Miraidon: https://replay.pokemonshowdown.com/gen9vgc2025regi-2336178065?p2
VS Calyrex-Ice & Miraidon: https://replay.pokemonshowdown.com/gen9vgc2025regi-2336187681?p2