Tactical Advantage is a gear perk that raises your weapon damage against blinded enemies. It rewards using smoke and other blinding effects before you open fire.
Shots against a blinded enemy hit harder. Blind a group, then finish them quickly while they cannot see you.
Wear the Caveira Vest in the chest slot. Gear perks are fixed to the piece of clothing that carries them, so you get this one by wearing that piece, not by unlocking it in a menu.
Smoke Grenade Pocket gives you more smoke grenades. Tactical Awareness on the Caveira Beret tags enemies through walls.