There are two main ways to approach using Dantes: as a highly stable burst-oriented DPS, or as a highly damaging stall Servant. Both are pretty conventional in terms of ideal team comp, but Dantes brings something unique to each one, resulting in a style of play that’s not quite the same as your typical ST Quick.
For a burst-focused Dantes, you want triple-Skadi. Doubling up on Summer Skadi is marginally better than doubling Caster Skadi, as Summer Skadi brings more NP-relevant buffs, and Dantes has two Buster cards with which to leverage her Buster crit buffs. There’s little complexity here: you use Skadi buffs for damage, Skadi batteries for charge, and Dantes cards whenever you can. It should be trivial for Dantes to use his NP three (or maybe four) times running. Against a single foe, this means you won’t even start taking damage until Dantes is through his burst window, so even if that doesn’t kill, you only have to survive two or three turns of attacks before you have Dantes’s skills and the Skadis’ buffs off cooldown and can do the whole thing again. There won’t be many conventional ST fights that can survive two full Dantes DPS windows, and at the point that’s insufficient, the fight probably wants you to stall anyway.
For a stall Dantes, you run Castoria with either Caster Skadi (for slightly more stability) or Ruler Skadi (for slightly more damage). In a typical Castoria/Skadi shell, you want to use your DPS’s NP every three turns, as part of a Skadi->DPS->Castoria NP chain. Dantes, though, is a little different. Assuming you’re fighting a single, stunnable enemy, you want to use Dantes’s NP whenever you can, even if that means losing a hit of Castoria’s Solemn Defense when you do ultimately have it ready. Generally, the optimal approach is to have Dantes keep NP-ing until you don’t have enough battery or refund to let him continue to loop, at which point you use a Skadi->Castoria NP chain to buy you some time while Dantes rebuilds towards his next NP. This will be faster and safer than typical Quick stall strategies, since every Dantes NP is functionally a turn of absolute protection.
Dantes is a super self-sufficient unit, too, so he’ll do okay even in lower-end teams, despite the fact that Quick Servants typically struggle in budget contexts. For budget Dantes teams, your top priority should be facilitating NPs from Dantes, since more Dantes NPs means more safety. Hans is a nice partner for Dantes for this reason, as are usually-Arts-leaning picks like Xu Fu, Asclepius, and Paracelsus. Prioritizing Dantes’s cards leads to a good amount of damage ramp on its own, so you can afford to sacrifice the damage you might get from a usual Quick-leaning budget support (like Barti) in exchange for more Dantes NPs.
Assuming that you can kill quickly enough for the damage demerit to not be an issue and that you aren’t having issues looping, the Black Grail is Dantes’s best CE. Dantes has no in-kit NP damage buffs, and none of his preferred supports bring NP damage up, so BG’s NP damage buff is pure multiplicative benefit for Dantes. For the same reason, Heaven’s Feel is a good alternative if you don’t have BG or are worried about Dantes’s survival. If you’re having issues looping or are running a budget team, you could consider something like Traces of Christmases Past instead—it’s a lot less damage, but between the starting charge and the extra push to Quick cards and NP gain, it can help keep Dantes NP-ing, which in turn helps keep your party alive.
There’s a clear best choice for CC type for Dantes: burn. Every burn CC on one of Dantes’s cards is an extra 10% supereffective damage applied to Dantes’s NP each time that card gets used. There’s nothing else you can get out of a CC that’s worth more than that, and there’s nobody else who makes better use of the burn CCs. Give them to Dantes! You won’t be disappointed.