Figured if no one was building with Cress I might as well throw something together; here's a build that I've played a couple of games with and has worked out decently well although more testing would probably be appreciated to refine the sets.
Building process
Cresselia often invites in Dark and Ghost types, the latter of which is why I think it pairs well with Gambit and the former meaning that Gambit checks/counters are appreciated such as Phys.Def Moltres and Bulk Up Tusk. I originally had a Sp.Def Garg over Amoonguss, but both Cress and Gambit really appreciate having Tera and Garg felt pretty bad without it, while the rain MU was also horrible. Specs Wake is a generally great breaker (shoutout the Basedlord for Molt/Wake) with very good typing that lets it come in on mons clicking Water moves into Moltres and Fire moves into Amoonguss, and you have potent stallbreakers with Cress/Gambit. Amoonguss is just a very good defensive mon in general with the ability to shut down a threat with Spore, a different move such as Foul Play could be used over Clear Smog but the team otherwise does not deal well with setup. Jolly Kingambit could be run for opposing Gambit, since this mon is as usual very threatening despite several checks being packed for it.
The team does not have hazards; Stealth Rock over Bulk Up is an option on Tusk, but an alternative win-con that beats many physical mons is appreciated. The Tusk EV spread is pretty arbitrary but I like it for outspeeding Ghold/speed tying Jolly Bax while not feeling as weak as a max HP max speed Tusk, and Ice Spinner over Knock is a good option that I prefer on most BU Tusk. Knock support is nice, though Knock would likely be best used if you swap BU for Rocks since removing boots is pointless without it. This set, maybe with a more defensively-invested EV spread, would likely make a more solid defensively oriented team but I like an extra win-con too much personally as I generally prefer more aggressive builds.
Threats
I got packed up by a rain team when I tried this with Garg over Amoonguss, if you're struggling vs Wave Crash a Phys.Def Amoong might be better but Sp.Def helps a lot into Greninja and opposing Wake and you do have a pretty good Crash quad resist with your own Wake. I also ran into a Tera Fighting Pult that caught my Gambit off guard, although Cress won that game; This mon is genuinely disgusting as I was in a pretty horrible position, Tera'd, clicked Calm Mind once and just instantly won as I'd earlier burned their Landorus-T and Pult with Moltres so Banded Dragon Darts was doing 20. You have good Enamorus switch ins in Amoonguss and Moltres, and Moltres is also a good Valiant answer, CM-Tbolt is tough but Amoonguss serves as a backup check since Val usually picks Shadow Ball 3rd to not be walled by Ghold. Bax is another scary mon which I was initially Tera Steel on Cress for, as this walls dual STAB and is immune to EQ, but being weak to Fighting is very bad so I much prefer Poison's resistances and single weakness to Psychic. Tera Flying on Gambit and Water Tusk helps deal with Bax but it's still pretty shaky, although Cress often can eat even a +1 Tera Dragon Glaive Rush and do a large chunk back with Moonblast. There is no great counter-lead into Samurott-H either as Amoonguss lets spike go up for free, but not much doesn't unless you lead Tusk which is not recommended as even at +1 Def you still take a lot if they choose to Razor Shell and other mons on the team appreciate having Tera more. Unburden Sneasler is very tough and is one of the main reasons for Phys.Def Moltres aside from Kingambit, Cress can set up a CM and kill it with only 60BP Stored Power though Tera is needed for the Tera Dark Night Slash set.