3- Every spin gives you a chance (about 5%) to win a card from the deck you played against (beside pillars). This also means that winning against a highly specialized deck will give you much higher chances to win cards.
The chances of winning a pillar are incredibly low. When THE RNG selects the cards to be spun, and finds a pillar as the outcome, it grabs a new card. It does this up to 5 times.