Leveling is completely different from end game. So you should expect to not fully understand your class at the start. You don't have to play efficiently or even correctly to level your character. I could spam frostbolt on my mage until I dinged 100 and do fine. But I wouldn't make the cut in raids.
Of course there's rarely any new blood. The game is 12 years old. I can't think of any game I would ever check out that was 12 years old unless I had played it previously or had a friend who did.