Here's my "I Don't Have To Care About Anyone But Myself" UI for my level 40 mage:

pUI_2.0

This Thread at Elitist Jerks is a great place to browse for any ideas, or just to see how UI's are built overall for your class/Role

http://elitistjerks.com/f32/t23417-share_your_interface_-_read_first_post/

Combet & healer based UI's tend to be worlds apart in design(also some on EJ are minimalist to the extreme)

 and the link to my Current UI screenshot:

/node/1177 

Here's my full UI, feel free to inquire about what's what.

Friks UI: Herro Crew...nice to see u in WSG ...IF misses u.

  DPS UI

Aidin's NuUI

Healer UI

IRC Fun Times:
[15:27] Dragonfork: aidin hates me this I know, for my repair
bills tell me so. many times my health is low, aidin laughs when i
explode.
[15:27] Dragonfork: yes aidin kills m

Start with three things: A unit frame mod like pitbull, a bag mod like Arkinventory, and a bar mod like bartender.  You can add more later, but start with those three.  Once you get those setup how you like them, add in Grid for raid frames (I'd put this first if you were a healer), and fubar for all the little odds and ends - just go through all the fubar addons and grabs what you like.  At some point you may want to get something like EEpanels to help with visibility of certain other UI elements.