My suggestion would be to buy a couple of decks, just to bulk out your collection and get a decent number of trainer cards, and to add to that with a decent number of boosters. My local gaming shop offers 5 boosters for the price of 4, so every week on payday I go and pick up an extra 5 booster packs. I only started collecting again a couple of months ago, after years of not playing, and already I have about 750 cards (mostly from boosters).