The easier way to get in touch with the Drupal 8 API is to port a module from Drupal 7 to D8.
This way you free yourself from defining architectures, tackling hard problems and just focus on the API changes. Making this a really great start for coders.
This talk will touch the changes made on the most used hooks, compare D7 and D8 code implementations, show links of useful documentations and some tricks and tips.
We want to pave the path for your migrations and to D8 itself.

Migrating modules to D8 is easier and funnier than you think, and a great way to learn the new APIs and contribute to see D8 reach a stable version sooner.