For the new people:
- The ranked grind will be difficult. Don't play casual mode; it is not casual in there because there's no actual matchmaking rating in effect. Play ranked mode and see how far you can get. You will improve with time, more cards, and knowledge of the meta decks.
- Try every class and level them to 10 as you will get quest gold and unlock new cards for all those classes. And it may also give you a feel as to which class you enjoy the most, which cards you might want to get and also if you have the patience to play the game in its current noob-unfriendly state.
- Before you jump into Arena, try to check out a few arena streams and see how they draft and play. I'd recommend Hafu, GuardsmanBob, and I'm hearing about another really skilled guy named ratsmah.
- The biggest issue right now for new players is that Arena only rewards the GvG expansion packs. This is a huge problem for new players as there are far more "required" cards in the Classic packs and Naxxaramas adventure. You have to buy Classic Packs with gold now and that sucks. If you are inclined to spend money in the game, buy the full Naxxaramas adventure and go and enjoy that. I highly recommend dropping the $25 or so for that (time is money and ain't nobody got time to grind 3,500 gold for all of Naxxaramas).
- I would recommend not to craft any cards for awhile. You can find servicable soulbound alternatives and you will understand how your deck works and will get a feel for what you truly need down the line.
- While you can get a Legend worthy cheap deck with Deathrattle Hunter and Zoo Warlock or some other deck you can find on the internet, experimenting and playing the game on a clean account can be really fun.
- Add some of us to your friends list. You can now spectate friends and it does make the game more enjoyable if you are not Skype screen sharing. I play mostly Arena and have a 5 win average and over 2,600 arena wins so that's a lot of experience. Kiro#1584.
- Good luck and have fun.