Play whatever you feel you might like, start on Normal difficulty (or lower if you're really scared), and READ what people say, decisions are important in this game! Save often and in different slots.
Have a group that can deal with different problems. A tank to hold the line (Barrik is great, he has AoE taunts), a healer (Lantry is great) and 2 damage dealers, I think it's best to have 1 melee and 1 archer or mage.
Be ready to adapt, for example against Bane type enemies you will need to change your tactics, they are very dangerous! Maybe you'll want to take a mage that can do bonus damage to them or a certain performer who has just the right song for Bane.