factz...fam Jay-Z used to rock a 10K cuban link so it's really all about the "why", if it's an investment piece (aka you sell dope and wanna hide your cash, yeah go 18k-24k and add quarter carat diamonds at least in VS1-F quality. they will always retain their value) now if you want something to wear everyday and your active, go 14K-18K, if 18K make sure it's thick with thick prongs/setting to hold any jewel.
also, diamonds aren't necessarily the most valuable stone you can use, rubies and sapphires can be pretty valuable depending on clarity and color saturation/hue.