Just keep playing Arena would be my advice, that's how you start to know which cards are better than which, and its also fairer as you don't need a great deck of your own to start with. My first go in Arena I didn't win a single game, these days average 3 wins I would say, and for that I get a card pack, some dust and some gold.
It costs 100 gold to buy a pack of cards, or 150 gold to enter the arena and you are guaranteed a card pack even if you lose every game, and more than that if you win a couple or more, so it's pretty much a no brainer to go to the Arena rather than buy packs IMO
Hmmm alright then so whilst it costs me £1.99 for two packs of cards in normal play mode, £1.49 gets me an Arena entry and I'll get a pack of cards even if I totally fuck everything up?
Up to now I've only spent £1.99 on two packs of cards, but I can quickly see myself racking up the costs if I get hooked on Arena, 'cause I'll be buggered if I'm going to grind out gold for entries.....
Still, I've cancelled my WoW subscription until the next expansion comes out so I could logically spend £10 per month on Hearthstone Arena entries and not be any worse off overall
I don't think I'm totally rubbish at the game, just had a match against another mage where it was totally obvious he was holding on for his Flamestrike on Turn 7, so I whacked him around enough before that to guarantee victory even though I knew he'd destroy my entire minion line-up on Turn 7.
I've had a lot of matches that had far more subtle strategies than that going on, I win comfortably (or opponent concedes) and I think to myself 'Yeah I'm getting the hang of this' but then I have a couple of matches where I'm pounded into the ground and decide maybe not.....
Fantastic game though, the amount of properly enjoyable time you could get out of it without spending a single penny really is to be commended (a mate at work has been playing it since the closed beta with his missus and they've not spent a penny between them and have never really felt stymied) - so it's nice to see Blizzard getting the Free-To-Play model right.
That aside though, I think they'll made an absolute fucking fortune with it - some folks just aren't going to be able to resist the lure of buying new packs of cards and other goodies. Me included probably.... Gonna wait for the full release before dropping too much cash though.