The Fairy and Flying-type Pokemon Togekiss is not the most common Pokemon to have in Pokemon GO, requiring both 100 Togepi Candy and 100 Sinnoh Stones to evolve into.
Still, those who do have Togekiss own a reasonably capable Fairy-type damage dealer in both the Ultra League and Master League.
Togekiss's niche deals with just about any Dark, Dragon, or Fighting-type Pokemon. To this end, it makes excellent use of Fairy-type moves for both its Quick and Charge moves. All stats referenced here are for PvP, so results in non-PvP may vary.
A Pokemon's move set would usually differ whether they're on attack or defense (defending a gym). However, Togekiss is one of few Pokemon whose optimal moveset stays the same regardless of whether the player or an AI controls it.
Charm is Togekiss's Quick move of choice. This Fairy-type move has a DPS of 10.7 and generates about 4 energy per second (EPS), letting Togekiss quickly ramp up to its Charge move while still dealing solid STAB (Same Type Attack Bonus) damage.
With a sizable 31.4 DPS, Dazzling Gleam will shred all Pokemon that are weak to it. It does take 50 energy to use, so Togekiss will be using Charm for a goon number of seconds beforehand. But once Dazzling Gleam comes out, the opposing Pokemon will be in a world of pain unless they resist Fairy-type damage.
Alternatively, Togekiss could be outfitted for a Flying-type move-set as well, but Togekiss's Flying loadout is significantly weaker than its Fairy-type setup. The setup for this would be for Togekiss to have Air Slash as its Quick move and Aerial Ace as its Charge move.
While still a competent selection, this Flying-type setup is decently weaker than the Fairy-type's, making it the less desirable choice unless the player needs explicitly a Pokemon with Flying-type coverage.