Hmm IMO I don't really like Spellfire or Dragon's Eye on Gwen(spellfire is ok sometimes ig), I feel like Gwen is a "mobile cannon"(someone said that somewhere and it fits perfectly). She does a burst of damage, then reloads(waits for her CD) and is kiting/avoiding fighting the entire time to keep her passive(you should have a tanky jungler) with a stun in the middle of the night or whenever you need to use it. Personally, my build would be Shatterglass, Clockwork, Reflex Block, either Journey Boots or Halcyon Chargers, and maybe Eve of Harvest and Broken Myth or another Shatterglass depending on the situation. Also, I would add that while Skedaddle does block negative effects, it doesn't block the damage so you could still potentially die.

Finished some minor edits. Will continue to expand the guide later.

So it looks like the recent update rendered my guide obsolete. I'll be sure to edit it tomorrow.