I am no expert, but a few years ago I decided to get my wardrobe in order and here are some things I did:
-Invest in a GREAT pair of black pants. I'm kind of a cheapskate when it comes to clothes so buying $245(!!!!) Theory pants seemed insane to me. BUT they are great, make me look and feel amazing, and they are good quality so they last. (But I've also bought a pair at Banana Republic for $75 that look pretty good.)
-Have at least one great blazer. I got one that is pretty basic, black, and another one which is more on the funky side, to mix things up.
-Have some basic color tops - cream, brown, black, and also some color so it's not too boring. I get my long sleeve Tshirts at H&M and Banana Republic (for the nicer ones).
-No trends. This was my rule - no skinny jeans or any of that silly baby doll top thing. Can't imagine that can last long. BUT when I feel like I need to wear something fun I run to H&M or Target and get a trendy piece there for under $20
-Invest in a few cashmere sweaters - they last, they are always in fashion and they feel and look great.
-Great shoes make the outfit. I didn't use to believe this, but now I do
I am sure Susan from the Working Closet Blog will have some great suggestions - have you checked it out?