I'm normally big on DXE, but I just started using Bigwigs this past week and I like it a lot.
I will go back to DXE when they bring some of the features that bigwigs has. ie.. how many oozes have been killed and are on the floor (not absorbed). And timers for heroic madness.
I'm a bit of an addon enthusiast so if this is too much it's all in personal preference:
DBM or something similar.
If you're melee, GTFO is helpful.
Some sort of raid frames. You would not believe how many wipes could've been prevented if the person who started an encounter had raid frames up to see that hey..a healer left..
- A bossmod (DBM/DXE/Bigwigs, pick one that you like, they all do more or less the same)
- Enabled raidframes (If you are a dps or tank, the standard raidframes are just fine. If you're a healer, get Grid or Healbot)
Advanced:
- Anything that helps you play your role and/or class better. For example, if you play a tank it's useful to have an addon that makes it easy to track what you have aggro on (Threatplates for example) or if you play a druid/DK/lock, an addon that shows who has their resses up and/or is using them to ress someone is useful.
- Kind of the same as the above point, but if you play a dps you should definitly make your UI in such a way that you can track those things that are most important: Runes, Combo points, Energy.... Or Dot timers, buff durations, etc. Make it show all the stuff you NEED to see, and HIDE all the rest. Less is more.