Hi, my opinion, FWIW. Dont buy shards. It's a waste of gems, or more precisely, a potential for a huge waste of gems.
I'd use them for masteries personally. If you dont want to grind minos for centuries. I'm taking the advice of all these fine people right here when they said to me get good farmers up in masteries, so you can take other champions in minos one at a time, and hopefully farm mino 15. All scrolls will go to the chaperoned..every one else should be maxed
(Edit)
In fact my wife threatened me if I were to spend money on this game, but she bought me a gift card for our anniversary.... hm?
So I bought the daily gem pack, just for masteries mind you.
Aaaand I bought some shards too... got my first soul bound, rest were really not worth it... lesson learned for me