For work/job interviews/professional functions I have two trusted Armani suits:  A pant suit in black, and skirt one in brown tweed.  They both have one button so it's flattering for a petite person.  Thank God for these suits!
 
I'm much more capricious and impractical when it comes to going-out outfits, so I'm afraid there is no favorite or basic in this case.  However, I do like to build an outfit around shoes.  I don't think I own a lot of shoes so I would consider them basic enough?  Like my fellow TFSer's, I am very fond of Manolo, Louboutin, Lanvin, Balenciaga, Marc Jacobs, and Prada.  They are all in constant rotation so I assume they are the basics in my wardrobe?  
 
Finally, I'm much more of a hopeless bum than I wish to sound! 

 Since this is a fashion forum I do feel the duty to speak more 'fashionably'.  Most of the time (these days), I actually wear j-crew sweaters, yoga pants, and Uggs.  Since I've been working from home, I am free to indulge in comfort.  Oh, how I will miss these days when they come to end!