The Gestures in the game unlock largely as you play through the game naturally. However, some are locked behind important side quests. You will need to progress through Drustan’s side quest to get the likes of the resting gesture, and you will need to complete the Byron and Iron Wayfarer quests to get the others. There’s also another missable one in the Shrine to Adyr, which requires you to go through a path in the umbral from the bridge you fight the Ravager boss in Fitzroy’s Gorge. It will eventually lead to a path that goes directly to a temple with the Shrine to Adyr and a vestige inside it.