In the Doctor Who show Gallifreyan is the fictional language of the Time Lords, which reside on Gallifrey. On the show, the constellations of circles usually don't mean anything. Doctor Who and the concept of a circular language called Gallifreyan are © BBC. I have no affiliation with Doctor Who or the BBC. This guide shows the different ways of writing Gallifreyan.
At the moment, only Sherman's Gallifreyan is available. Doctor's Cot and Rasilonian Gallifreyan guide will be coming as soon as I have time. I'll try to add other systems too, but it might take some time. Contact me for any questions, requests, or criticism.