>>27011669Certain products come with a code that nets you a specific card. Each of the tins in pic related, for example, have a code that gives you its respective card online.
The versus ladder also has specific cards you can earn. Other than that, your only choice is to buy/redeem/earn packs or to trade.
But trading should get you 99% of what you need and for very cheap. Prices are not high at all for an overwhelming majority of the cards.