Getting started with gmaps4rails - a simple map with a single point centred on London, UK

gmaps4rails_example_1.html.erb

<%# Shows a map centred on London, using the default marker/pin image. %>
<%= gmaps4rails([{:lat => 51.51, :lng => -0.12}].to_json) %>
<%= yield :scripts %><%# Usually yield :scripts goes just before the closing body tag %>

gmaps4rails_example_2.html.erb

<%# Shows a map centred on London, using a draggable custom marker image *and* shadow. The shadow is optional. %>
<%= 
  gmaps4rails([{
    :lat => 51.51, :lng => -0.12, :draggable => true,
    :picture => image_path('/images/custom-marker.png'),
    :width => 100, :height => 60,
    :marker_anchor => [50, 60],
    :shadow_picture => image_path('/images/custom-marker-shadow.png'), 
    :shadow_width => 150, :shadow_height => 60, :shadow_anchor => [50, 60]
  }].to_json)
%>
<%= yield :scripts %><%# Usually yield :scripts goes just before the closing body tag %>

If your use case is simple, try using the Google Maps API directly. In the end I didn't use gmaps4rails, everything I needed was easier to do client-side with the API directly. This is left here in case it helps others.