I speak for myself only, but if it was the first time using nostrgram and like it, a notification about support will be enough: if you like, support type. Then I see settings and chose an option to support for ... time. There wont be any need for extra adds about it on main screen. And another notification when time due,a bit like subscription really. The subtle engaging and choice has a better appeal for me. However not sure how that will work with people with a lot of notifications. So should be flagged somehow indeed without being annoying. Maybe for any client kind of notifications.