Black Market is a dark place, it not named dark for nothing. If you want to start your walk down rabbit hole, you would have to need some ultimate guidance and knowledge. For example, you will need some appropriate deep web gadget for browsing tor network anonymously, like tor browser and a lot more. Or, you would have to accept different habits for exploring dark net, not to allow footprints.
Hopefully there is few sites created to guide you through complex world of underground deep web hidden from the surface. This one is the best one i know http://darknet-markets.site/
Darknet-markets.site - is an ultimate usher through the world of dark net.
It got what you need : best onion, the full guides for security, guide for tor marketplaces, darknet reviews, new, updated and legit onion marketplaces mirrors.