Notification appears saying "X has added a gift to their list" etc. Prompts users to come back to the app and increase retention. Also possible that they put that gift on someone else's list too. I don't think the notification should ping for if someone adds something to someone else's list as users would get too many notifications. I also think there should be some sort of cooldown, so if someone adds 5 things to their own list in a span of 10 minutes the user doesn't get 5 notifications. Maybe after a gift is added, wait 30 minutes to see if another is add and then if not send the notification out?