Bone Dragon and Titania don’t really have synergy, and i’d say, in the long run, you are better off investing in Titania then the Dragon.
She’s a more well-rounded, more versatile troop.
For now I’m spending the stones only when I’m sure I really need to max the troop, this is why I’m asking for a good team. The only team I have maxed it’s a rockworm one.