How a witcher school set is built in The Witcher 3
A school set in The Witcher 3 is a ladder rather than a single suit. Basic, enhanced, superior, mastercrafted and grandmaster tiers each need the diagram of the tier below, so the whole line has to be crafted in order and a set is never finished in one visit to a smith.
Each Witcher 3 gear set covers four armor pieces and two swords, and only the grandmaster tier carries a set bonus. Griffin favours signs, Cat favours fast damage, Bear favours heavy defence and Wolf sits between them.
Witcher 3 sets beyond the four schools
Beyond the four schools, The Witcher 3 also holds Viper gear from the prologue, Manticore gear from Blood and Wine, the Tesham Mutna and Hen Gaidth vampire pieces, and the Forgotten Wolven set added in the next-gen update. None of them follow the full five-tier ladder.
Every diagram a set needs is on the Witcher 3 crafting diagrams page, and what those diagrams consume is on the crafting components page.