Ruby Level-Up
First and foremost, code style. This is one thing that people look for first, and no matter how well designed your classes are - a misplaced indent is just unacceptable. Ruby doesn’t have a style guide as solid as Python’s PEP8, but the most commonly followed one is https://github.com/bbatsov/ruby-style-guide. Also, checkout Rubocop to automate these style checks as part of your CI process.
Learn to use rdoc (https://github.com/rdoc/rdoc) properly. Get used to viewing the generated HTML documentation for your code. It is important that readers of your code are able to ‘grasp’ the big picture of what your code is about - well-structured comments make that easier. Also, look into http://www.literateprogramming.com/ - Even if you don’t go all the way, a lot of those principles could be useful.
Make sure your Ruby basics are clear - especially important if you discovered Ruby through Rails. I’d recommend ‘The Well-Grounded Rubyist’ from Manning publications.
Get a hold of common web frameworks