Dress pants go very well with a turtleneck for a formal dress because turtlenecks have long been worn as an alternative to neckties and shirts. When wearing casual outfits, your turtleneck can go with both jeans and chinos, dressing down a turtleneck shouldn't be a problem because there are so many amazing casual outfit ideas available on the internet synching turtlenecks with jeans, chinos, topcoats, and jackets.