For a beginning player, or someone just starting out with addons, I'd recommend keeping things simple, and sticking to addons that just change the Blizzard UI or add a small feature or two, rather than completely replacing it and adding hundreds of features like Carbonite.
If you're looking for something that will make it easier to see where to go to complete your quests, check out
TomTomLite. It will add a rotating 3D arrow to your screen that points you toward the nearest quest objective completion point (eg. the ones you see if you open up the world map).
If you're looking for something that will make it less tedious to pick up and turn in quests, try
Blitz.
I also use
QuestMyMap, which cleans up the quest display on the world map a lot.