To unlock the Dressed for Success trophy in Shadow of the Tomb Raider, you will first need to complete "The Price of Survival" DLC mission.
Once you have finished "The Price of Survival" mission, fast travel to a base that will allow you to equip any Outfit -- Kuwaq Yaku Ruins in Kuwaq Yaku for example. When you are there, equip the Silent Sting - Scorpion pistol and Hunter's Array - Apex outfit. The Raptor's Eye skill will be obtained by completing the challenge tomb.
Once you have equipped the pistol and the outfit, exit the camp and the trophy will unlock.