Hearthpwn

on hearthpwn, check the "Forums >> Quests and Dailies" section and complete all the freebies within your means.

with the gold, hold on to it...  definitely refer to some resources (streams, heartharena.com) on navigating the arena.  try it once and see how you like it.  now, 3 wins can net 1-2packs which is really worth it in terms of expanding your collection quick, but the difficult part is to pick up playing on arena.  regardless try it once to get a feel of some of the cards you don't have.

TLDR: for now try arena once and make the best of it, and don't be discouraged if you lose 0-3.