Gainz Box Coupon: $7 Off Your First Month! Posted by Hello Subscription on February 9, 2020. Subscription Box Coupons & Deals / Gainz Box Coupons Hello Subscription may earn compensation via links in this post. Read the full disclosure Save for Later Notification Gain[z] Box has a new sale! Get $7 off your first month! Just use the code GZBX7. Valid to new subscribers only. Get $7 off at Gain[z] Box! Are you getting Gain[z] Box?