You can play pretty much anything, I myself built a pretty inefficient party when I played the game, because I didn't really know how to build a character properly and how the class schools synergize with each other, but I still managed to finish the game just fine, even if a lot of fights were somewhat of a slog.
But I guess I could try giving you some basic tips on character building I picked up later by checking various other builds and the skills you can learn in the game.
1. Don't spread your attributes between multiple damage sources, only specialize into one of the three (strength, finesse, intelligence). This one is somewhat obvious, but if you feel like you want a character that uses both magic and melee, it just doesn't work. Same for learning skills that scale with an attribute you don't spec into, it's a waste of slot most of the time, unless the skill has some really good utility.
2. Check the bonuses of all the schools, they don't apply only to the skills they let you learn, but they affect everything, for example the bonus from Huntsman works with spells too.
3. Check the skills of other schools than your character uses, there are usually utility skills that work with any class and it's sometimes worth putting that one point into said school just so you can learn the skill, just be sure it doesn't scale with a stat you don't have or that it gets resisted by the opposite armor to your main damage type (unless you intend to use that skill to help your other party members). This is how you usually build a hybrid character, you specialize in one school and pick utility skills from others.
Anyway, there's a mechanic in the game that let's you craft completely unique skills you won't get from anywhere else than crafting. The game doesn't even hint at such possibility iirc, so it's a good thing to know. You could probably try to figure the recipes out yourself or just look it up, I myself found the recipes kind of counter intuitive and had to look it up in the end.
