If you're a thrifty shopper, your best bet is this Leith Shift Dress. It's a terrific item, while not very pricey. Another strong contender for your wardrobe is this Missguided Shift Dress. While the price of this piece is not very high, it will certainly attract a lot of attention. You may also want to look at this MinkPink Shift Dress. This item is not expensive either, but it will make a difference in your wardrobe.
For something in the middle of the price range, you're in luck with this 3.1 Phillip Lim Shift Dress in stock and waiting for you. You are guaranteed to fall in love with this product.