So this was posted on the subreddit and thought I would share. Not sure if everyone here uses it.
The way this works is using Amazon Coins to purchase cards which is offering a 30% kickback for a limited time. You also need an Android tablet - might work on phone. If you don't have an Android device, you can use DuOS (free 30 day trial), an android tablet emu...
1. Purchase Amazon Coins
2. Download Hearthstone on your Android device THROUGH THE AMAZON APPSTORE, playstore didn't work for me.
3. Purchase packs, you should notice a 30% coin kickback on checking out with the Amazon Coins.
4. buy more packs.
It should be noted that the kickback only works on the 15/$19.99 packs and above, so the more you buy, the better. I bought 100$ worth of Amazon coins for 90$ and got 102 card packs.