Unless you live in a hot climate, a coat is your best friend come autumn and winter. What style do you prefer? Is it a classic fitted style, a cozy oversized coat or a trendy duster?
If you're a thrifty shopper, look at this Asos Coat. It's a fantastic piece for a reasonable price. Also check out this Coat. It's an item you'll love which also doesn't cost too much. You might also want to consider this Asos Petite Coat. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.