It's better to buy all of the adventures first(starting with Naxx) and then to spend gold on arena/packs, in my opinion.
It is a pay to win game since in order to do well you need the legendary cards that you won't get unless you've opened 150+ packs. I , for instance, have never came across a single Twilight Drake or any of the Giants, having opened around 45 packs total. The only useful legendary (to a degree) that I've got from packs so far is Cairne and I crafted Dr. Balance with dust, which made me shed a tear.
Reading up on arena strategy so I don't waste my free arena use. I've read that paladin is a top tier draft class, and I think it's one of my 3 options, so that's nice and dandy.
depends on what you call doing "well". I've gotten to rank one using an almost all basic card Zoolock.
Welp, I read your offer a bit late. 1 win because I completely forgot about mana curve and minion to spell ratios. Didn't even get any half decent cards out of the pack it gave me <.<
Oh arena, how I love thee.