If you're not planning on spending much, your best bet is this Classic Shirt. It's a wonderful piece, while not very costly. Another great option is this J.Crew Button-Front Shirt. While the price is not too high, be sure that this piece will become a worthy addition to your wardrobe. You might also want to consider this Rails Button-Front Shirt. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.