Each class levels indepently of each other and get it's own atribute points. If you hower with the mouse over each atribute in the character screen it will tell you which one is for what - basicaly first three are for physical attacks, next three for magical and so on. Some for close some for ranged so find the most usefull combination for each given class. For the Gladiator you'd prefer to have increased closed ranged / mele attacks - Strenght - and if you feel like some to Vitality as well.