Leveling up: Some moves are learned automatically as Gardevoir levels up. You can check its movepool in-game to see which moves it learns at certain levels.
TMs and TRs: Technical Machines (TMs) and Technical Records (TRs) are items that teach a specific move to a Pokémon. You can find these in various locations, purchase them from vendors, or receive them as rewards.
Breeding: Certain moves can be passed down from parents to their offspring through breeding. This requires the parent Pokémon to know the move and have the "Egg Moves" property.
Move Tutor: Some Pokémon Centers have a Move Tutor who can teach specific moves to your Pokémon for a fee. The available moves may vary depending on the game and location.
Specific Events: Occasionally, special events or limited-time promotions may offer the opportunity to learn unique moves that are not available through other methods.
Note: The availability of specific moves for Gardevoir can differ depending on the Pokémon game you are playing. You can consult the game's official guide or online resources for a complete list of moves for Gardevoir in your specific game.