Tougher Turrets is a gear perk that makes your auto-turrets more resistant to damage. Turrets last longer under fire, so they hold an area or cover you for more time.
Your auto-turrets take less damage, so they stay up longer when enemies focus them.
Wear the Electrician's 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.
Only if turrets are part of your plan. Otherwise a defense perk in the chest slot helps more.