One of the only differences I've noticed is installing mysql is slightly different.

Step 1: Install XCode Command Line Tools

xcode-select --install

Step 2: Install and prepare Homebrew

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
brew doctor
brew update

Step 3: Install rbenv

brew install rbenv ruby-build openssl

Step 1: Install Ubuntu

Step 2: Add a deploy user and optionally a user for yourself.

Assuming you're logged in as root add these users and login as "not root."

adduser deploy
adduser [yourname] #optionally
vim /etc/group
# add your users to the sudo group like so: 
  sudo:x:27:isaac,deploy
vim /etc/ssh/sshd_config
# add to file or if they exist set the flags to no.

1. Create your gem:

Here is the most modern approach to gem crafting:

bundle gem gemname
cd gemname

edit your_gem.gemspec and add description, summary, required gems and optional website. Add required gems for development such as rspec, rails or minitest to the Gemfile.

2. Add testing framework:

RSpec:

rspec --init
touch spec/your_gem_spec.rb

Minitest:

# Rakefile

Very little has changed since Mavericks but here's an updated tutorial.

Step 1: Install XCode Command Line Tools

xcode-select --install

Step 2: Install and prepare Homebrew

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
brew doctor
brew update

Step 3: Install rbenv

brew install rbenv ruby-build openssl

Tell you model to serialize it as a struct and create a setter to build the struct on create.

# post.rb model
serialize :content, OpenStruct
def content=(v)
  self[:content] = OpenStruct.new(v)
end

Then you can add any form elements you want for content.

-#form partial

= f.fields_for :content, @post.content do |ff|
  .field
    = ff.label :name
    = ff.text_field :name
  .field