FanDuel is a widely used Sportsbetting and Casino app. Their referral bonus is usually $25 but is temporarily $125. Please use my referral code: Join me on FanDuel
You need to sign up, deposit $10, and bet that $10 on any game. You will then instantly receive the referral bonus.
I have also written a step-by-step explanation in this Google Doc:
Comment in this thread if you have any questions!