In MTG 2014, each deck you unlock comes with only 10 out of 40 cards unlocked. To complete the deck, you ought to win several games, each win unlocking an additional card. For 22 decks, including the expansion, that sums up to 660 wins total.
A grinding strategy seems to be advisable.
Since the campaign levels vary a lot, each deck would perform best at a different level, I assume.
So: What would be a good/best level to gain additional cards for each deck?
A google search is of little use, I get mostly sealed-deck strategies. Maybe my Google-Fu is too weak.