What to do with gold in F2P account?

Hi there. I have a F2P account, with naxx and some good GvG cards, altough I don't have Dr. Boom. Got almost no cards from TGT and don't have Blackrock adventure. What do /hearthstone/ suggests?

I have some few options:

• Arena (I can maintain a score that if I lose, I can at least get a pack and 50 gold)
• Packs (which ones?)
• Adventure