The world of type is huge. From my studies, most professional designers have their favorites. And it is not necessarily a large library. I’m a font collector and have far more than I need. Eventually, you find classics that you love. This takes time and also studying the work of others. So there isn’t necessarily a simple answer and it will be different for each designer you ask.
Here’s some food for thought:
1) What do you want the readers to feel? Use your best adjectives to describe this feeling when they look at the work. (Playful, corporate, whimsical, rustic, traditional, etc)
2) Is there a theme? It could be historical, geographic, cultural, etc.
3) Have you printed your own “Type Book” for the font families you own? Do you know the difference between display type and type families?
4) Are there photos or illustrations that are used? What are they like or how are they treated? Do they have a style or era?