When going for a casual job interview, think sharp and modern attire. From semi-casual to super-casual, a suit is always the best choice, but you'll want one that has a little more edge and style than your basic black suit.
Don't let the name fool you. Casual job interviews are not indicative of casual attire. Your goal is to look fresh and trendy, so a basic black suit isn't the first choice. Instead, opt for a colored suit in grey, tan, taupe, or (dark) blue, such as this Calvin Klein Tan Texture Slim-Fit Suit. From the color suit you choose, go on to pick out a shirt and tie that complement the color of the suit. In general, lighter colored button-up shirts are best, matched with darker colored ties. For the tie, don't go crazy, but you can add a little variety such as with dual stripes.