Edit: so apparently it’s only per money spent, 1 card per 10$ (yeah I didn’t resist and put 20$ to on Bloodborn for my last orb to get the extra gold). Sorry for the misinformation.
On a side note, it’s a pity cards are only available this way.
Duelyst now drops Steam collectible cards :>
The first series features all twelve generals with their official artwork and the short description of their portraits in the Armory. Cards are clickable for an higher def of the artwork and a background specific to Steam (not much change, but something exclusive is something exclusive).
Cards are currently sold for around 0.13-0.14€ in the Steam marketplace.
Collecting all twelve unlocks the Steam badge ‘Initiate’ and 100xp!