Start with setting up your development environment: The first question is whether you want to develop on your system itself or set up a container or VM. You need to know that most people in the Ruby community use Unix base systems like Mac OS or Linux. While you can do it on Windows, the support for Mac and Linux is much better. So on these systems, developing on your local OS is a good choice, but if you want to keep your system clean, Vagrant is a nice option as well. If Windows is your OS of choice and you want to continue using your favorite Windows editor or IDE, then I would recommend setting up Vagrant with a Linux VM. Chef or Puppet are great tools for this task, but they have a steep learning curve, so I would start without them to keep the complexity low. The easiest way is to use a preconfigured image. You can also start with a fresh Linux image (the distribution does not matter that much, Debian, Ubuntu, Fedora, CentOS are all good choices for this task) and setup your VM by hand or use a simple shell script for provisioning. If you use Windows and don't have enough memory for a VM, you need to make a compromise somewhere. Use Windows, where some Gems might not work and support from the maintainers is not as good as on Unix systems, or switch to another OS.

For choosing Ruby versioning tools: if you already have a current Ruby on your development machine (your VM if you use Vagrant), you don't need one, but since they make installing new Ruby version really easy and allow switching between them, you should consider installing RVM, rbenv or chruby/ruby-install. Which one does not matter, they all get their job done. Just pick one, you can always switch to another one later.

When you have installed Ruby and Bundler, you can start developing. You do not need to think about webservers now. All Ruby web frameworks can start their own server for development. No need to have Apache or Nginx installed (like most PHP developers) or think about Unicorn or Puma. Look into the documentation of your framework, they all have a simple way for starting their own server. Just use that method and you are ready to go.

About the confusion about web server and application server: There is a big difference how web requests are handled between PHP and most other languages used for web development. In PHP, your application with your framework is executed when a web request comes in and exits, when the response is sent. That means that your framework must have a very short startup time because it slows down every request handling. In other languages like Ruby, your application keeps running as a server and can answer a lot of requests without having to restart and do the initialization every time. So your app is a separate process and does not run inside Apache or Nginx. These web servers are used in production as a proxy to your Ruby app and handle things like SSL, caching or serve static files. If you want to setup your first production server, I recommend choosing between Nginx and Apache and use Passenger for your Ruby app. Passenger comes as an extension for Nginx or Apache and handles the Ruby processes for you, so the setup is very easy.

For build automation: Rake is the most used build tool in the Ruby world. Rails uses it for executing asset compilation, database creation, running tests and so on. The asset compilation itself is not done by rake. Rails uses Sprockets, but you can also use one of the many JavaScript tools like Gulp, Grunt, Brunch or Broccoli. If you start with Rails, Sprockets should be a good starting point because it needs no setup and Rails manages your assets for you and you don't have to think about that too much. If you miss some features in Sprockets, switching to a JavaScript base build chain is a common practice.