the new essence for unbreakable bond

can someone explain how they work. how far u can level before moving on to the next one and so on cause it's nice we got something new but don't know much about it other then u spend money and dia on it and it gives nice boost in br depending on how far u got it leveled.

cause all i do is get them and 1-click and use them all up but don't know how far u have to go til u get to the next circle i am at lvl 16 on essence of glass right now.