What can be won in the arena?
You get up to 5 rewards on completing 12 wins or 3 losses. One reward will be a card pack. The other one to four rewards are random (dust, gold, single cards). More wins = more and better random rewards.
What is the minimum price received when loosing 3 times?
You always get your card pack. The worst random reward is "5 dusts". However, there is MMR matching in arena. You should expect to win at least one game on average even if you're terrible at picking cards.
When accumulating gold through daily's what is the best way spend this gold?
- Dailies in play mode generate 1 pack per ~3 games.
- Arenas generate 1 pack per 5-15 games played.
- Games in Play mode without dailies generate 1 pack per 30 wins (now limited to 1 per day).
There's two extremes of player here: Some players complete the dailies and log off, sometimes going for multiple dailies at once (3 or fewer games per day). On the other extreme, others play at least two hours or more each day (8 or more games per day).
- If you value your time highly (as the first group does), doing the dailies in play mode generates more gold than arenas. Arena purchases wouldn't get used, so packs should be purchased instead. You may want to set aside 300 gold in case you get an extra burst of playtime so you can arena on those days.
- If you value your time playing at a net of zero (as the second group does), doing arenas generates more packs than play mode.
This depends on time available and skill.
Infinite arena is considered the best way to get cards and dust. However, even assuming you can consistently get 7+ wins, it's bad for actually earning gold. 7 wins typically earns you between 150 and 180. If you don't factor in the free pack and the bonus prizes, that's 10 games, drafting time and risk for less gold than the 3 games/10g.
8 wins isn't much better, 9 is actually worse (you get more cool stuff) so you'd really need 10 wins in a reasonable number of those 7+ runs for it to be worthwhile.
On the plus side, infinite arena is actually infinite. There's no cap so you could play 24/7 if you want.
Quests are the most time-efficient method. Assuming you are capable of using at least 5 classes, you can reroll everything to get Domination quests and get 60g most of the time. Assuming a 50% winrate, this takes 10 games to earn 60g+20g for the 3 wins quest if you play an extra match.
Timewise this would take about an hour and a half, assuming just under 10 mins/game.
Once you've beaten your quest, your only remaining option is the 3 wins quest. This is slow- earning you 10-20g per hour. However, you can use it to supplement the quest rewards. The method above earns you 540g per week (80/day) so winning another 6 games pushes this to 100. This is enough for 700/week or enough to buy naxx wings as they are released.
Since you can play whatever deck you want here, this may be quicker than winning the quests. About an hour, probably. In total, that's two and a half hours a day.
So, to summarise, reroll your quests to 60g, beat those then beat the 10g/3 games quest to make up the rest of the money you need.
Best Answer
As of the new patch, the arena will only reward you with GvG packs.
If you want regular packs, you'll have to buy them from the store.
The original announcement states that "Arena rewards now give Goblins vs Gnomes card packs instead of Classic card packs"