Gainful Coupon: Get 15% Off! Posted by Hello Subscription on March 17, 2019. Subscription Box Coupons & Deals / Gainful Coupons Make the first comment! Hello Subscription may earn compensation via links in this post. Read the full disclosure Save for LaterGo to commentsNotification Gainful has a new sale! Get 15% off your purchase when you use the coupon code SAVE15. Get 15% off at Gainful! What you’ll get: Are you getting Gainful?