I've been writing this run as a short timeline.
Started off in 769 by knocking off an ahistorical character and starting as a Visigothic lord named Gundemar, Count of Roussillon in-game but Lord of Perpenya in-character.
A brilliant strategist and a man of towering ambition and anger, Gundemar was never fond of his nominal liege of lieges, King Karloman of Middle Francia, nor of his liege-lord, one Guillaume the Cruel, set in Toulouse as Duke over that city and Marquis of Gothia, with reign over all of Septimania. Discontent with the Frankish dominion over the lands he felt rightfully belonged to his people, he set to work expanding his control over the coast. His campaign began in 771, when Carcassonne came under his influence. Over the next decade, Gundemar extended his formidable reputation and protection to the cities of Narbonne and Maguelone. By the time he was finished, he was more influential in the region than his own overlord. With the consent of the church he established himself as the Count of Roussillon, and while Guillaume was still de jure overlord of the Marca Gothica, the nobles there de facto owed their allegiance to Gundemar.
Driven by the schemes of his nobles to support his claim to the Gothic March, and with the support of several bishops, Gundemar declared that Toulouse was by right a part of Gothia, and he marched on Toulouse with 2,000 men, besting the armies of Guillaume in the field. In 784, with Guillaume falling prisoner to Gundemar's forces, Gundemar crowned himself Marquis of Gothia and Count of Toulouse. In recognition of Guillaume's supreme martial account, he released him from the gaol and gave him command of an army, but eventually grew tired of his scheming and drove him from his lands altogether; Guillaume would eventually resurface as Count of Burgundy.
Through the 790s, Gundemar extended his reach steadily, claiming lordship over Venaissin and Gevaudan and extending protection to the Bishop of Vivarais, then wresting the County of Foix from the rebel Peranudet. It can be said that Gundemar's court was one of the earliest melting pots in which formed the culture that would be called Occitan. Shortly thereafter, the Francias came under the unified rule of Karloman after the king of West Francia, Charles the Tormentor, died without male heir, brought low by severe stress.
Karloman outlived his brother by just seven more years before being struck down in 804 by Viking raiders under Ragnarr of Helsingland. This left Karloman's 13-year-old son, Karloman II, on the throne in his infancy. Gundemar, at that point serving as the marshal of the Frankish armies, administered the defense of the Frisian coast against invading Norsemen under Hogni of Sweden, then turned back the raids of the Viking Oddr against Normandy.
The period of peace did not last long: Dissatisfied with Karloman II, Gundemar and several nobles in the south of Francia moved to recognize Gundemar himself as the rightful lord over Aquitaine and Vasconia. A stout war ensued over the next three years as Occitan and Visigothic men-at-arms routed the Franks in a series of running battles along the Garonne, then stormed the gates of Paris and sacked the city, forcing Karloman to acknowledge Gundemar as King of Aquitaine. The decree of kingship was ignored in the west, where the Basque landlords of Dax and Armagnac continued to acknowledge Karloman II as their suzerain, as did the Count of Limousin.
Two years later, Gundemar passed away in his sleep and left everything to his only son, Gundemar II - a less militarily able but more patient man with a better eye for dealing politely with his vassals.
I'm actually about seven kings in and have a bunch of these written up.