From time to time you might see a message on Twitter or Facebook or on Global Chat announcing bonus gold.
For example "Bonus 5 gold for 2-player wins this weekend!".
To make sure you are receiving the bonus, you need to:
1. Make sure that Notifications are Enabled.
2. When you see the notification announcing the bonus gold, you must tap on it so that Spellcraft opens and reads it - that's the only way Spellcraft knows about the bonus.