If you don't want to install ruby package on your machine and you are familiar with Heroku you can use Devstep.
Devstep reuse the same buildpack as Heroku, in short Devstep will start a container and install wagon inside. If you want to drop wagon just drop the container, nothing have been install on your host. (Devstep demo video : https://vimeo.com/99482658)
First install Docker : https://docs.docker.com/engine/installation/
Then install Devstep : http://fgrehm.viewdocs.io/devstep/cli/installation/
Now create a new project
mkdir MyPortfolio cd MyPortfolio devstep bootstrap -r devstep/MyPortfolio
Devstep will start and open a new container, now set the environnement type
build-project -b ruby reload-env
Now install wagon and bootstrap your new project
gem install locomotivecms_wagon wagon init . -t bootstrap bundle install
Your image and your project is ready, just exit the container to same the image (no more build for the next dev)
Image is ready, it's time to hack !
devstep hack -p 3333:3333
Now you are inside a container, with all dependency installed, let's run wagon
bundle exec wagon serve
You can access to your website at http://localhost:3333
Note : Devstep can hack a lot of environment (python, js, go....)
If you already have a website project, you can simply start to hack with the following command
git clone https://github.com/myaccount/myproject cd myproject devstep build devstep hack -p 3333:3333
Enjoy it !