I agree with the several posts that suggest playing WoW without AddOns for a little while. Some AddOns have a tendency to take over a player's game play, and that can be pretty detrimental to your development as well rounded player.
That being said, the WoW UI has some very serious issues (the element placement is horrible at best, et cetera). You should begin introducing AddOns when you are unsatisfied with the amount, and way information is being presented to you.
For example: If you find yourself losing track of the cooldowns on your spells, then you should invest in a cooldown tracker that suits you. If you find that you can't keep track of enough relevant data, because the UI elements are in the stupidest places ever (can you tell I hate the default UI?), then get an AddOn that addresses their placement.
There is a
section on these forums where users may get help in locating specific AddOns. When the time comes, I am sure you'll find the needed help there.
Good luck starting WoW, and have fun!