In my mind, this means you should look for a dress you really like and can wear for a long time, but it doesn't mean you need to spend lots of money either. Observe:
I think the key to versatility is a good quality fabric that isn't too sheer, but also not too shiny. You can rely on accessories to bring the glamour, and the dress can rise to the occasion. However, you should avoid thin cotton, jersey knit, and any smocking or elastic. I regret to inform you that this rules out most (but not all) of what you'll see at Target and Old Navy, although the latter has some amazing eyelet dresses that are nicely made and look great!
Here are the dresses I featured, in case you're interested: