Hearthstone is Lots of Fun. Free-to-play cardgame from Blizzard. Good fun, and you can earn gold to pay for more packs of cards pretty easily. If you’re not playing it, give it a go;
http://us.battle.net/hearthstone/en/
I’ll post some tips on getting gold and cards I’ve found. First is about Questing;
Questing
You get a new quest every day which gives you a certain amount of gold. What some people don’t realise is that you can cancel a quest once per day and get a new, randomly allocated one.
I normally have limited time so I tweak my quests every day and once I have 3 I have at it for a serious session. With a bit of nouse you can align the quests (so you might end up with 2 quests that reward you for playing Priest and another for summoning lots of critters). So when you get to play you get loads of gold .
Herring's Fishbait 