Gwen wins fights by staying active longer than her opponents. Her build must allow her to survive long enough for her DPS and sustain to take over.
Ruby Crystal
AP omnivamp in extended fights, with perfect synergy for E attack speed
AS + AP on-hit, amplifies the DPS auto with E boost
AP scaling on the R Needlework and the passive True Damage
Plated Steelcaps
Glorious
Q Snip Snip! repeated inside of the W Hallowed Mist stack Conqueror quickly.
Magic shield contre mages that try to the poke outside of his Hallowed Mist.
Passive sustain the fights to profiter of the passive Thousand Cuts.
Accumulated HP to she is hard to kill during his split-push and dives.
E (Skip 'N Slash) dash triggers penetration magic during his engages.