@Vero I took a crack at parameterizing the URL and path as well as adding the user-configurable keywords. For my own usage, I wanted 2 keywords (one for opening directly by name, one for searching). When you type "gem", you see both search and open options in the results and you can either arrow down or type s to search, which feels intuitive to me.
Let me know how this looks: https://github.com/manewitz/rubygems-alfred/releases/download/v2/rubygems.alfredworkflow