In Rage of Bahamut on the Android, iPad, iPhone, and iPod Touch, once you get done with the tutorial, you have a chance to enter a referral code to get some free stuff.
That free stuff means 50,000 free rupies, and a rare card called Angelic Knight, which is a decent beginner card with 930 atk, 770 def, and only costs 6 power.
Do not skip this opportunity, because you can’t go back and use a code once you complete the tutorial.
Enter this code to get your free rupies and rare card: xbb51409