Another way is to let chocolatey manage your ruby package (and any other package), that way you won't have to put ruby in your path manually:
Install chocolatey first by opening your favourite command prompt and executing:
@powershell -NoProfile -ExecutionPolicy unrestricted -Command "iex ((new-object net.webclient).DownloadString('https://chocolatey.org/install.ps1'))" && SET PATH=%PATH%;%systemdrive%\chocolatey\bin
then all you need to do is type
cinst ruby
In your command prompt and the package installs.
Using a package manager provides overall more control, I'd recommend this for every package that can be installed via chocolatey.