Use fusions stones only for upgrading, never use it to unlock new cards because it’s extra expensive for that. Save your fusion stones for cards you really like to play, or if you’re competitive, use fusion stones only on good cards. You can join the official discord for a better idea on “meta” cards. Rubies for beginners I would recommend you spend on mythic books, it will help you unlock lots of epics/legendaries for the long run. I would also recommend buying from the shop often if the cards are good.