Welcome to the Grishaverse!
According to the quiz on the Grishaverse website, I'm a Materialki (Alkemi) as well, but I self-identify as a Corporalki (Healer).
I don't know which Grishaverse books are my favorite. I'm on the less popular opinion side, but I really, really loved the Grisha Trilogy except for the end of Ruin and Rising. King of Scars is good, but it was advertised as a Nikolai book when really it should be the Nina and Zoya duology. Six of Crows is great and I love all the characters. The plot is exciting and the twists are unexpected but brilliant.
My favorite male character (and character overall, for that matter) is the one and only Nikolai Lantsov (Major of the Twenty-Second Regiment, Soldier of the King's Army, Grand Duke of Udova, and second son to His Royal Majesty, King Alexander the Third, Ruler of the Double Eagle Throne, and King). My favorite female character... I don't know. I love Alina because she's really relatable, Zoya because of her no-tolerance-for-nonsense policy, Nina because she's all-around awesome, and Inej because she's so good.
Again, welcome to the Grishaverse!