One of the best ways I have found to stretch your wardrobe is to use pieces that you wouldn't immediately associate with work wear, but combine them in an appropriate way. As I have two wardrobes (work and fun!) I often move certain items around and find new ways of encorporating them into my daily wear.
With the weather turning slightly chilly I have started wearing one of my favourite ensembles - a blouse/shirt and dress. In this case I took a satin long sleeved tunic (which I usually wear with a thin belt and leggings) and a plain black dress, which shows of the decolletage, but is long enough to still look sophisticated.
Dress (actually knee length, but my weird posing has made it ride up) and Tunic both from ZARA (I really never realised just how much I have purchased from ZARA over the years, I need to branch out)!
So yes, here we have it. Party-wear to work wear through layering, particularly useful if you are planning an evening out and can't face the fuss of changing (or are lazy like me).
I think it works, what do you think? Now if only I could figure out how to make those frilly, strapless Summer dresses office friendly... ;).