Also, is the "Ruby on Rails Tutorial"[2] the definitive book about learning the Rails framework after learning the Ruby language? Could you suggest it or something else?
[1] https://www.amazon.com/Ruby-Programming-Language-Everything-Need/dp/0596516177
[2] https://www.amazon.com/Ruby-Rails-Tutorial-Addison-Wesley-Professional/dp/013804984X
[1]: https://www.humblebundle.com/books/ruby-rails-pragmatic-prog...
Other than that, here are many great books about ruby and online resources.
[^1]: https://pragprog.com/titles/ruby5/programming-ruby-3-3-5th-e...
Jeremy maintains both Roda and Sequel gems and his advice is very practical IMHO.
It's maybe not the first book you'd want to read but it's full of good ideas for once you've mastered the basics.
1. https://www.packtpub.com/product/polished-ruby-programming/9...
It looks like maybe it's paid now, I don't know. Hartl's tutorial was my introduction to ruby, rails, and TDD all in one go. It's a great tutorial, he's a great instructor. I would recommend anyone to start there. If it's paid, in hindsight, I would have paid quite a lot for the tutorial the first round. (Also, maybe you can find an archived version and learn with an older rails, if money is a concern?)
Ruby felt easy for me to pickup. I think Rails was harder to learn than Ruby.
Have fun!
Edit: Also, a bunch of rails nerds were talking in here today, maybe they left some thoughts about how they started: https://news.ycombinator.com/item?id=38248421