Outline Flat (code Generated) Mesh

Hello,

I am trying to create a spell indicator so a player knows where their spell will land. Currently i have the mesh generating but cannot figure out how to outline it.

Ive tried every shader i can find online (its not something i really have the time to learn) for example:
http://wiki.unity3d.com/index.php/Silhouette-Outlined_Diffuse

Below is my mesh in wireframe and solid.. i think the issue is that my generated mesh has duplicate vertices but im not 100% positive.

https://www.dropbox.com/s/cwqfdmgj96v32t9/example.png?dl=0

Any help or advice would be appreciated.