The open front cardigan is perfect for transitioning from summer to fall. A chunky cardigan will look great with a basic t-shirt and skinny jeans.
If you're a thrifty shopper, your best bet is this Asos Open Cardigan. It's a wonderful piece, while not very expensive. It is also worth considering this Open Cardigan. It's a product you're bound to love which also doesn't cost too much. You might also want to consider this Brave Soul Open Cardigan. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.