@AccessDenied
I went through the same process as you a few months ago and I was able to find much of what I needed between these sources:
The docs: https://docs.nodebb.org/en/latest/ (google searches will often send you to out of date versions, watch the urls!)
The source: https://github.com/NodeBB/NodeBB (Having a good IDE helps with making sense of the source and doing good searches)
I got a lot of help from purchasing Webstorm IDE (https://www.jetbrains.com/webstorm/) I've also heard people here like using Sublime Text with a lot of plugins installed.
Finding any existing plugin with related functionality to what I was trying to do was very helpful. For some reason, I found the Mandrill email plugin really helpful at first (https://github.com/akhoury/nodebb-plugin-emailer-mandrill), but just dig around until you find something with functionality related to what you are trying to do.
Lastly, I'd search and ask questions here under the plugins category (https://community.nodebb.org/category/7/nodebb-plugins). I've asked a lot of newb questions and the community has been awesome.
A few more notes. When I was first interested in Javascript and Node.js about a year ago, I went through a bunch of tutorials online. I found this one to be very well done: https://github.com/workshopper/learnyounode
Also, after developing a few plugins myself, I wrote this Slush based tool for generating NodeBB plugins based on a number of questions:
https://www.npmjs.com/package/slush-nodebb-plugin
Good luck!