Every time a card has been received, hit the compare button. If the card is an advance, keep it. If not, add it to a set. If it does not belong to some set, auction it or quicksell it. Keeping it organized saves double-digit hours over the duration of the year.
Don't dare sell or auction off a single card until looking at the sets first. Some of the places can be earned entirely through single-player challenges while some may be gradually earned with even a small bit of luck during the year.
This is a great way for players not seeking to break the bank to deserve the same cards as others who sell their automobiles. With a little bit of patience, then add any additional players to some set. Even if the reward is not an upgrade, the reward constantly sells for more than the total of the components to make the card.
It is healthy to avoid the store entirely since cards get slowly better as seasons move on and cash spent at the store for cards today will be money wasted the moment the cards of tomorrow are released.
But it's that the limited-time cards which are the largest waste. They are tempting because the battles simply give enough to almost complete a set for a fantastic card, however, this great card will not be so good whenever the upcoming limited-time event hits.