Ruthless Challenger Armor Set

The Ruthless Challenger armor set can be purchased for 3,500 Tech Fragments + 500,000 credits per piece from the cosmetic Tech Fragment vendors in the supplies section of the Fleet, as of update 7.0. This set is wearable by characters on either faction at any level on any class.

Tech Fragment Armor

Tech Fragment Vendors: These armors can be purchased directly from a vendor callled the Cosmetic Armor and Weapons vendor (Z9-V86 droid) in the Supplies section of the Fleet. The versions from this vendor are Bind to Legacy. These armors do not change between factions and you can buy all 32 sets on either side. Each piece costs 3,500 Tech fragments plus 500,000 credits, so a full set is quite expensive, but is accessible even to free-to-play players if they save up and buy the set piece-by-piece.

How to Get Tech Fragments

GTN: These older armors were originally available in Galactic Command boxes in the 5.0 expansion, so you may be able to find the Bind-to-Equip versions left over from the previous expansion on the GTN from players who had extras leftover to sell, though they will likely be hard to come by, and expensive. The ones on the GTN seem to be the same as the ones on the Tech Fragment vendor, though I can't promise they don't change appearance, so make sure to preview them before you buy them on the GTN.

Legacy Bound

Legacy bound armor is armor that can be transferred between your characters on your server. Pieces of the Ruthless Challenger set can be obtained on one of your characters, and then sent to another one of your characters on the same server. you can also stamp Legacy-bound armors into the Outfitter tab for as many of your characters as you'd like without the item being stuck on one character.