Where can I find existing sets of stories, rules, etc? Is there a library or database? I’m looking for something that can handle casual, chitchat-y conversation well. 
“rasa init” will create initial files for you. Check Sara or several demos in rasaHQ github repos.
Thank you! Sara is a good start, but I’m still looking for examples of rasa bots that are less transactional and more about maintaining a dialogue.
Give it a shot, take a look at my Dadbot (in Spanish 
), I have also integrated GPT-3 as a custom action.
This is EXACTLY what I was looking for: