It's strongly recommended to have a warrior, mage, dwarf and elf (not too important which kind of elves), the remaining 2 characters are optional.
I'd recruit them from those four classes, a second warrior or dwarf and a second elf might yield the easiest game.
If you have two characters of the same class in a party make sure they have opposite genders so they don't look the same in combat.
I'd create characters with 13 in all positive attributes, negative attributes can be decreased at level ups and don't hurt much. Make sure everyone reaches maximized strength as soon as possible, combat stats are most important.

I recommend picking advanced difficulty.