Verène Haydé, Senior Enchanter of the Ostwick Circle and teacher to Sanea Trevelyan, is technically a veteran of six Circles in total: born in the Montsimmard Circle, taken to the White Spire shortly after, sent to Kinloch when her magic manifested, transferred to Kirkwall to avoid lingering anti-Orlesian sentiment, moved to Cumberland after her Harrowing (and Meredith's coup of the city), and then finally to Ostwick when they needed a Senior Enchanter.
That's CRAZY, damn! After seeing so many Circles firsthand, she must have some opinion about their effectiveness, no? Does she belong to any of the mage fraternities -- Aequitarian, Libertarian, Loyalist?
My three Circle mage OCs are Telhara Surana, Aeden Fletcher, and Oliver Pentaghast.
Telhara was a Dalish mage who was caught by Templars and brought to Kinloch Hold at age 17. She was pregnant at the time and gave birth to twins at the Circle, before they were taken from her. She stayed there until the events of DA:O when she passed her Harrowing, got involved in Jowan's escape plot, and was conscripted by the Wardens.
Aeden was born in Starkhaven and trained at the Circle there, eventually passing their Harrowing. After the Starkhaven Circle burned down in 9:31 Dragon, they transferred to Kirkwall for a time. (It sounds like they would've been there at the same time as Verène!) After that I think they spent a few years as an apostate, and then of course the Mage-Templar War started and all mages became apostates.
Aaand Oliver was first trained at the Cumberland Circle, but after a failed Harrowing (due to foul play) he was made Tranquil. He was transferred to the White Spire for a time and then eventually sent to the University of Orlais to serve as a research assistant.
I don't think any of them were active in the mage fraternities, but if they were, Telhara would have been an Isolationist, Aeden would be an Aequitarian, and I guess Ollie would be a Loyalist by default. After his Tranquility is cured, however, that's a different story.