You might try simply using the various lighting effects, without any geomtry. Use a bulb light (the effects are not available for all lights) and try the various settings for 'light sphere'. You can add lens flare if you wish. You can even use more than one light together to extend the range of effects. The image on the left uses two lights.

For a shape light use a plane, or some other shape and a texture map in the alpha channel. Then set the Glow channel to a color of you choosing and apply Anything Glows to the plane, choosing the Glow color for the light color. You can have a light shaped any way you want with this method. That's the method I used for the right-hand picture.