My .irbrc file

require 'pp'
require 'irb/completion'
require 'irb/ext/save-history'
require 'rubygems'
require 'wirble'

Wirble.init
Wirble.colorize

IRB.conf[:SAVE_HISTORY] = 500
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb-history"
IRB.conf[:AUTO_INDENT] = true

Don’t forget to install the wirble gem.

How to painlessly remove all gems

root:~# gem list | cut -d" " -f1 | xargs gem uninstall -aIx

How to prevent installing rdoc and ri files with gems

In ~/.gemrc file you need to add following line:

gem: --no-ri --no-rdoc