Books 2, 3, and 4. Spoilers ahead for School of Wizardry, but not so much for the other books.
Secret begins with Randal working in the stables as he is trying to carry out the quest decreed at the end of School: to find a senior wizard, who can give him permission to practice magic again. Without using a bladed weapon or magic on the way. At that inn, as a consequence, he's beaten by a knight who feels slighted, and rescued by another. To his embarrassment, because the other knight is his cousin Walter. Who then takes him on a squire. He goes on with the knights toward the tourney. After troubles with bandits -- and Lys finding them with directions from Madoc -- Walter is wounded at the tourney, and they all go on to find the wizard, to free Randal and heal Walter. This all involves dreams of animals, reading the wizard's diary, breaking into a tower they know has magical protections, recovery from a fire, and more.
Statue, OTOH, has Randal doing more typical journeyman things: wandering the world to learn magic. It opens with his meeting up with a former wizard apprenctice, whom he had met at the school, and who is now a carpenter. And then at the inn, he finds a dying man in his room, with a magical status, and a request to take this to another man. That involves magic, both from the statue and the one whom it's brought to, the details of how wizards must speak the truth, yellow-clad soldiers in pursuit of a thief, and more.
Danger opens with Lys and Randal performing for coins. Then they learn that Randal broke the law -- the Prince forbids all but his own wizard from practicing -- but he can get off by doing some magic for the prince. And Lys takes a job acting in the royal troupe. This involves a treacherous brother, lots of disguise magic, Randal's inhibition about some magic after the events in Statue, a prisoner, saving a captive he's been ordered to kill, and more.