Badges are add-ons to Costumes that will provide additional boosts. You can only equip up to three badges and you’re not allowed to equip badges of the same color at once. You can farm badges from the Costume Badge Dungeon, under the Growth dungeons category. The dungeon is limited only to three attempts per day and you can’t use tickets to have additional attempts unlike the Origin of Growth and Golden Time dungeons.
Also, unlike runes, you cannot enhance badges to increase their grades and stat bonuses. You can only sell unwanted badges. Replacing an outdated or lesser badge will still cost Gold, like what you do in runes. The higher badge grade you’ll replace, the more gold it will cost.