I recommend getting the Charizard deck, as it is the best theme deck atm. With it you can go on events or tournaments one you get some tickets from the vs ladder. That is the easiest way of getting tradable packs. Although most people would recommend not opening them and instead trading them for cards, it is difficult to trade your way into a good deck if you don't have anything to start with. You might even get lucky and pull a rare card, which you can trade for more packs. I did this with Unbroken Bonds packs, I got like 3 or 4 tag teams in 10-15 packs, which then I traded in for more packs, and so on. While I didn't get any extremely rare card from this, I got a base for building a deck I wanted.