Four legacy sets are available from the Dromund Kaas/Coruscant Vendors. The Renowned (legacy level 10) and Exalted (legacy level 20) sets are available for credits. They cost quite a bit, with prices ranging from 75k to 250k for a single piece (Exalted pieces usually more pricy). The Birthright and Inheritance sets (not moddable – level 14-16 and 29-33) are available by trading in tokens obtained via random drops. For more information on the location of the legacy vendors and a preview of some of the legacy sets not found here yet, please check out this guide here.
Legacy sets are also often available for a limited time during World Events. They require Social Rank I or Reputation with the Gree. Most of the Reputation gear is also Bind to Legacy.