Hearthpwn

Lots of people have said it, but I have to reiterate. Classic is the best value for a new player until you have a good collection. Then I'd get the first wing of BRM, all of LoE, and then get some WOG packs to throw together a decent C'thun deck. It's not impossible to get 100g a day if you are lucky with your dailies, and always reroll the 40g ones. The only time you don't want to do that is if you have synergy between them. Like, if you have one to win 2 with mage or priest, and another to win 5 with priest, all you have to do is win 5 with priest and you've got a good chunk of gold.