In what should I spend this?

There's this event currency, I don't know in what should I spend it. I know the grey one you can get a new descendant. So far I only have viessa and bunny. Any recommendations? The pink one I have no idea. Also I have no idea how to use the energy activator and crystalization catalyst. I got those as an attendance bonus. Oh and thanks for the help in the last post. This community is great ♥️