Alexa, tell me how to build a skill
medium.com
medium.com
The biggest thing I've learned about Alexa Skills developing them is that people will say things differently (shocker!). So, take time to think through your intentions and offer many, many, many different implementations of the same phrase (utterances). This prevents people from getting confused, or labeling your skill at buggy; when in reality it just wasn't expecting what they'd say.
For Bitcoin, I am not into crypto currency, but that skill was done on live coding session, so I needed something that people like and that I can integrate really fast.