CSQ stages also seem decent for XP for the time being due to having a 30% discount on their stamina price. I managed to gain a few levels off of clearing the CSQs for the Knights in my active set of squads without using a stamina potion.

However, secret gardens don't show up after clearing a CSQ stage so the only rewards will be tier 1 gifts and 2* Knights. On the other hand there are quests tied into the number of CSQ stages you complete so picking up the earrings for every Knight you're using does more than give them small attack/defense bonuses.