readme: add missing stuff

README.md

@@ -6,17 +6,19 @@ A student-run organization at Binghamton University created to foster a communit
 
 In addition to cloning the HackBU repository, you'll need a few things to run HackBU locally:
 
-1. **Ruby** - Ruby is a programming language powering our build tools. Ideally you should install the version in [`.ruby-version`](.ruby-version). On *nix, you can use [asdf](https://asdf-vm.com/) to manage Ruby versions:
+1. Install the necessary dependencies to build Ruby: https://github.com/rbenv/ruby-build/wiki#suggested-build-environment.
+2. **Ruby** - Ruby is a programming language powering our build tools. Ideally you should install the version in [`.ruby-version`](.ruby-version). On *nix, you can use [asdf](https://asdf-vm.com/) to manage Ruby versions:
 	```
+	$ asdf plugin add ruby https://github.com/asdf-vm/asdf-ruby.git
 	# From the project repo:
 	$ echo "legacy_version_file = yes" > ~/.asdfrc
 	$ asdf install
 	```
 	This will build Ruby and cause your fans to ramp up, so maybe don't do this in class.
 
-2. **Bundler** - Ruby's package manager. Comes preinstalled with Ruby as `bundle`.
+3. **Bundler** - Ruby's package manager. Comes preinstalled with Ruby as `bundle`.
 
-3. **Jekyll** - Run the command `bundle install` in the project directory to download and install Jekyll. (~~Try using `sudo bundle install` if you run into problems.~~ <-- do NOT do this!!! you will litter your system with files, if it even lets you)
+4. **Jekyll** - Run the command `bundle install` in the project directory to download and install Jekyll. (~~Try using `sudo bundle install` if you run into problems.~~ <-- do NOT do this!!! you will litter your system with files, if it even lets you)
 
 You can start the Jekyll server with `bundle exec jekyll serve --watch`. See the [Jekyll documentation ](http://jekyllrb.com/docs/home/) for more information.