These are the programming languages, libraries, frameworks and tools we work with
For learning React, we have no special (free) resource to recommend. A search engine can be of help here. Wes Bos provides an awesome free Redux course. He also has a paid React course. In order to learn Redux-Saga, the docs of Redux-Saga are a really good starting point. Knowing Redux already might be of help before reading the Redux-Saga docs.
Most of our backend is written in Ruby and uses Ruby on Rails. To get a first impression of Ruby, Try Ruby should be your first stop. Other than that, CodeCademy provides a free Ruby course to help you getting started. For Ruby on Rails we recommend the Rails book.