Well, my main country in the fantasy world I've created functions a little differently. Around 90 years ago, there was a major rebellion against the old aristocracy that was orchestrated by Audorian sorcerers once they were outlawed for their unnatural ways. The Audorians made the whole thing possible but not without help from four other distinct power blocs. After the dust settled, each power bloc formed a mercantile / quasi-hereditary House that would jointly rule the new country. Each House is obviously flavored by the particular backgrounds it came from but each house is branching out into different livery companies and many members are either originally from other Houses or from particularly talented or rich merchants or the spontaneously magical (sorcerers from non-magical lineage) so there's both less differences between the houses and more differences within the houses than one might first suspect.
House Rosentia: They were an old aristocratic family of hidden sorcery who supported the revolution against their noble brethren. Through their skilled betrayals, either by butchery, assassination, or simple espionage, they substantially weakened the old noble families. Due to their treacherous backgrounds, and many scandalous rumors of dark fiends in their lineages, they aren't trusted. However, they're high levels of fertility and the fact that any child born to a Rosentia will be magical has led to them being prize husbands and wives. Many other Houses quite greedily wish to have a Rosentia marry into their ranks (unfortunately, the special fertility stops after the first generation born outside of House Rosentia). House Rosentia has capitalized on the exoticism of their blue blood and their frequently strange appearance, and if they are not artists themselves, they often sponsor some of the best artists - from architects to dancers, painters to writers.
House Ansalon: A naval House who are now renowned for their chemists, alchemists, and sorcerer-researchers. This house is comprised of several prominent naval families who were captains of the old aristocratic fleet before they consolidated their power and helped launch a coup against the old nobles. They are now heavily involved in naval merchantmen and control many water routes as well as shipbuilding and seafaring guilds. They make most of their money in the spice trade. Many of their members are actually descended from pirates, privateers and even the fisherman trades, who were either capable enough or rich enough to be recognised as a member of this noble mercantile class.
House Delevon: Once upon a time these were a secret society of witches and hunters, some of which had the spark of sorcery, who used to creep around behind the nobility's backs and remove curses, slay monsters, and generally protect the general populace. The old nobility had little care for the outback towns and villages ... they were far too focused on their own stilted entertainments. When House Delevon saw an opportunity to seize power for themselves and orchestra change, they have taken it. Unfortunately, they still have to deal with the fiendish House Rosentia whom they would have preferred to see exterminated. Nowadays, they are more often hired for their abilities firsthand and have a huge network of witches and alchemists to call upon rather than be involved in most guild activities (other than, for example, wards). They are also quite skilled at dealing with sidhe, procuring magical artefacts from the Ihlander salt plains, and coaxing Places That Aren't into cooperating with the Realms interests.
House Carrington: The original mercantile class of nouveau rich that were never treated with the respect and dignity they had dreamed of under the old aristocracy. Really, they largely provided the financial and diplomatic backing. They gained a lot of power and prestige in facilitating legal debates, ensuring trade networks went as undisrupted as possible, and keeping the administrative machinery running even during a revolution. There were hitches but House Carrington maintains that it could have been a lot worse. These were the old bankers, lawyers, and budding professionals, such as physicians, alchemists and scientists.
House Audor: These are the remnants of an old sorcerous college that was brutally attacked and massacred by the old aristocracy. They came together and, utilising their most subtle magics, inspired a shock wave of revolutionary sentiment that took the nobility by suprise. They are academics first and foremost and where the old aristocrats awarded careful adherence to noble birthright, etiquette and carefully outlined hierarchy, the Audorians have an appreciation for intellect, rigorous scientific method (what they consider to be rigorous scientific method, of course, is not the same as what modern science would consider it to be), and a meritocratic hierarchy that is dependent on so many factors (intellect, publications, breakthroughs, magical talent, lineage, personal achievements, charisma) that determining one's position in the scale of things is really quite convoluted.
So there you have it, a look at the magocratic houses in brief.