RoaringBee

The tower gives xp to all participants regardless of how they performed. Training missions also reward xp to all units who participated, but it isnt a crazy amount. The only one I did was 30xp to all at the end. Certain emblems also have their weapons give 2x xp There is another way though but it requires getting a specific S rank bond ring before midgame. If you're mid-late game;

Each emblem has 2 specific bond rings that give a skill, with one exception who has 3. Only way to check in game is to have an A rank ring and previewing the S rank through the Meld Ring feature. If it has a skill, it will show it there, otherwise that specific ring won't have one.