The most general and important advice I can give you is: build things. If you're practicing by yourself, find a problem you want to solve. Be it a page component you're interested in (a navbar that hides on a threshold) or an entire, but simple, app (a downscaled Evernote clone), it's important to have clear goals and to be able to see the results of your work.
I'll suggest only one thing here...:
You folks heard me talk about thoughtbot enough already, but, geez! Their UPCASE platform is not suggested enough! It's the platform they use for training their teams internally. And they release most (if not all) of its content for FREE. I'm still going through their courses myself and I fully recommend you folks check it out.
If you're interested in learning TDD, check their testing section for 3 entire courses on the subject and many The Weekly Iteration episodes (a weekly program of them) on it .
Yeah yeah... you can read articles and tutorials. But nothing beats an actual book.
I used to suggest Sandi Metz's POODR as the first read after Wagon. But 99 Bottles (which she wrote with Katrina Owen) beats it now by a mile as an introductory material to OOP (object oriented programming), being a lot more practical and easy to follow for a beginner in both Ruby and OOP.
A bit of a recipe book. Read the summary and intros and maybe glance at it from cover to cover. But the important thing is to keep it nearby. Wondering how to cleanup your controller or all those messy validations on your model? How to validate a form object? You'll find here some of the best ways to leverage the power of Ruby and Rails to your advantage.
It's a thorough guide on JS. You can start by reading the first 10 chapters, which will give you the brunt and basics of the language. Chapter 11 can be a rough introduction to asynchronous programming, but it's needed if you want to build advanced front end interfaces (a basic level is enough for most projects). In any case, read this if you're interested in leveraging the best JS to offer and upscale your front end code.
Another entry from Sandi Metz. The one book that every new Ruby developer should read. It's packed full of content worth years of experience for the road ahead of you. It's likely you won't be able to apply most of it on your first projects, or worse, it's likely that your first tries to follow into Metz's steps are going to lead you to code that was better off before your refactoring attempts. But... DO READ IT. And DO MAKE A MESS of your code. The lessons you learn here are going to follow you for your whole career and they will eventually fall into place, giving you a much clearer perspective on how to approach complex problems.
Another recipe book. THE recipe book when it comes to design patterns. Written by the Gang of Four. Its examples are for JAVA and SmallTalk, but the structure of the patterns is agnostic and can be applied in any language. I often find myself searching through it and reviewing the implementation of my classes, trying to identify the best to solve the specific pain I have.
Wanna learn some spells? Here's your book. Metaprogramming is one of the most controversial subjects you can find, and it's arguably one the strongest super-powers of Ruby. But, as they say, those come with great responsibilities. You'll either find yourself writing amazing code with it, or the kind of arcane scribblings for which your coworkers will hate you. It's a great read since, despite the advanced and confusing subject, Perrotta managed to write the book as, believe it or not, an engaging story about your day job.
So... classes are actually instances of... themselves(?), and an instance doesn't inherit directly from its class? And classes are not actually classes? Yeah. Most of what you hear as you're starting with Ruby is an elaborate lie to simplify things. They're abstractly true, and help you think and talk about code seamlessly, but, under a microscope, things are a lot more complicated. Interesting read that will help you solve the pesky problems you hope you'll never have.
- How to build an App in a week - An amazing podcast episode with Ben Orenstein about building an app in a week.
- Refactoring Guru - Design Patterns - Offers a softer introduction to design patterns, with a very illustrated and exemplified approach. Haven't checked their book, but if it has the same level of care as their site it should be amazing.
- Rails Doctrine - What?! You haven't fully read it yet?
- Book and Courses Recommended by Plataformatec - That's the checklist you receive in order to join plataformatec (creator of devise and simpleform).
- Ruby Tapas - Short weekly screencasts for Ruby and Rails tricks.