You want the wave near your turret for good trades and to avoid all-ins with Gwen. Try not to push the wave when you are farming with q.

3Q>E max Avoid walking up to her e+q range. Gwen typically runs ghost or ignite in this matchup; you can run ghost as well if you want to match hers. She has strong all-in potential against you if you are not running ghost post six if the wave is near her turret. Ghost is optional if you are confident in your wave management. Wit’s end and Nashor’s Tooth are both viable options as first items. If you are confident, cull is viable.

You should avoid trading pre six, since you typically do not have the damage to beat Gwen in short or long trades unless Gwen makes a severe blunder. Post six, you can look to bait her into dashing and q slow her and get free autos off. Focus on dodging her q before doing damage. Do not step into her shroud for trades. Post six, you are heavily favored in short trades.