Newly Installed App (gem) Via Terminal, Path?
Ruby "Gems" are not generally applications, most often they are libraries. From the Ruby Gems website


  1.1 Really Quick Start Question: I’ve installed RubyGems and I want to
  install Rails (for example). How do I
  do that?
  
  Answer:

gem install rails

  
  1.2 What is a Gem?
  
  A gem is a packaged Ruby application or library. It has a
  name (e.g. rake) and a version (e.g.
  0.4.16).


(emphasis mine)

Also, see this information on how to inspect a gem:


  2.5 Looking at an installed gem When you run

gem specification  progressbar
# shortcut: gem spec progressbar

  
  you will see all the details of the
  ’’progressbar’’ gem.


You should consult the documentation which came with the gem, or, post more details so we can assist you more.