For starters my frugal wardrobe doesn't look cheap or mismatched (like a lot of unfrugal people think that just because I did't pay much for it that it doesn't look good). My trick is to build it slow with pieces that I'll actually wear.
My image isn't a huge thing for me, however I do want to look professional at work. Contrary to popular belief work clothes aren't any more expensive than others if you shop the right way. I wear a D cup so finding clothes that fit right is a huge challenge for me.
I have discovered that the Lane Bryant dress shirts fit me great almost every time. So, I watch craigslist and ebay for deals and stock up when I see something good. A few months ago I found a woman on craigslist who lost weight and was selling her entire wardrobe. I got 20 pieces of nice clothing for $50. That how much one Lane Bryant shirt would cost new.
For pants I stick with Old Navy (which can be found on ebay) or whatever walmart has. However I have a lot of nice item froms B. Moss. They have great work clothes, but are expensive. However they have great sales. I can usually get a $50 pair of pants for $10-15 and they last me many years.
As far as casual clothes I'm a jeans and T shirt person so whatever I can find that fits ok works for me....I'm going to be cleaning in it anyway so it doesn't matter much what it looks like.