There's no 5* Demon card.
Demon start only from 6* and evolve up to 8*
You can get two of them from Chapter 6+ as stage rewards, and from gem recruit\arena win.
http://dragonera.wikia.com/wiki/Monster ... 28_star%29There exist two topics that can provide some light into such questions:
One -
Things you can't buy from shop You can get this cards only from Gem Recruit and 4 of them from from Chapter 6+ drop.
And second -
Things you should buy from guild shopIt explain good cards you can buy from guild shop.
But to answer to your question about where to get all cards will be very hard.
You can get cards as drop, from shop, as reward from arena and gem recruit. And there's no system that explain all of this.
So it will be easier to ask about each card)
In general - you can get 4-6* from guild shop (with exceptions). And from gem recruit. And as stage rewards. And as drops. And as arena reward. And as ...
Midas aka Howrus. GM of Fairy Tails.