Whats your goal, HHC? Playing for fun or with ambitions to get legendary someday? If first, Murloc decks are fine. Shaman best hero for it, imo. But its also funny with a paladin, f.e. with sword of justice in combo and so on. But for those decks you need a lot of epic and rare cards, some leg is also not that bad. So, if you wanna save time you should play a cheap basic deck like hunter or maybe a mech mage. You will climb up easier and earn some gold to get the entry-ticket to the arena, to get boosters and from time to time, you can craft missing cards with your dust.
So its all up to my entire question.

And, if you like the game you also can think about buying some boosters. Dont see a problem there because it was free and if you have the money, no worries. It just gives you a nice starter.