I work for a cable manufacturer. For line level you really only need decent interconnect cables. Mic cables work just as well, but they are more bulky and expensive, so it's a bit of overkill.
I know the word "decent" is a bit arbitrary, but you want something with medal ends and where the jacket isn't almost as thin as the conductor inside. Plastic molded end cables won't end the world, but they don't have nearly as good of isolation and typically made to meet a price point rather than a high standard. Since it was mentioned, gold or nickel contacts won't make a significant difference that you'd likely be able to tell. Gold is more conductive, but its use is more for durability since gold doesn't oxidate or corrode nearly as fast as nickel. Still, this isn't something you're likely to worry much about. It's a nice feature, but not a necessity.
Price can vary dramatically, but more $ does not always equal better. Higher price can certainly denote more rigorous QC or better components, though the cost in components is fairly negligible in most cases. Most often it's just down to where it's manufactured and the cost of labor there. Good cables come from China, bad cables come from China, or Taiwan, or Indonesia, or Japan, or even the USA. You can buy an inferior cable made in the USA that's more expensive than a cable made overseas that's spec'd out, and visa versa.