one small thing that was bugging me with the Circle Outline texture is that even though the Surface Type is set to transparent there was the small visual bug of still seeing the square of the Quad.
A quick fix I found for this is in the Material under Surface Options, just enable Alpha Clipping and play around with the Threshold. I found that, for me, I like having my this set to just over 0.6+ so the center of the circle is also transparent to the player.