Discourse Foundation Resources for Beginning Plugin Developers

I recently received a Message from a member interested in writing a plugin for Discourse.

A problem for this member is, that although enthusiastic about Discourse, they are not well versed in Ruby.

I have seen many posts here of members with similar type problems.

That is, a member with a different background of programming experience comes to Discourse with little to no experience with the basics of a particular discipline.

To a large extent I have lost the ability to see the programming landscape from the eyes of a beginner and usually go to documentation. But I imagine there must be other sites that someone could go to

So other than this list, what suggestions could you make for someone that wanted to start from square one in getting up to speed in writing Discourse code?