I see that beginners have huge problems when they start and I believe that using defaults would make things a lot easier.
So what do I mean? When users only enter a title and not a display title, simply copy the title into the display title so that something is visible. If a block is required but not added by the user, do not simply show nothing in the preview. Instead show a default block with the information that a block must be used. This way, the user gets immediate feedback. Otherwise they are pretty confused why nothing has changed.