Saving Assets to Device

[timpeti]

The App is in an early stage so i don't need any code examples but just developer's advice:

The app ships with 10 stories and will be updated weekly with two new stories. All stories are accesible via thumbnails. I want to include all 10 thumbnails within the app for faster loading, while story content (mainly a video) will be fetched on demand.
Is it to save the thumbnails of new stories on the device to improve the next app loading? Is it even possible with the stories (videos)? How much space can I use? Can I get rid of outdated contents once stored on the device? What about not including the first 10 thumbnails but triggering their download (and storage for later uses) on first app load? Are there best practices for this kind of usual tasks?

Where can I find documentation on this topic?

Thanks for the advice
timpeti