How to counter Gwen
Let us take a look on how to beat Gwen. We will look at champions who are strong against Gwen and who are weak against Gwen. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Top champion who counters Gwen. You can already win in champion select with the right counters for Gwen. If you want to know how to counter Gwen then you need to take into account the best picks vs Gwen and the worst picks vs Gwen. This Gwen counter data is based on matches played by Pros on patch 14.23 and previous ones. It is important to see whether Pros counter picked Gwen or whether they played as Gwen.
Champions used by Pros to counter pick Gwen
Looking at the matches from Pros (see table Pros counter picked Gwen) we can see that they picked 
K'Sante most often to counter pick Gwen. The matchup K'Sante vs Gwen occured 31 times. Gwen has 14 wins and 17 losses in this matchup. Learn how to counter pick K'Sante to get another perspective on the data.
Lane outcome for Gwen
When looking at Gwen counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Gwen. The lane outcome of Gwen consists of three outcomes: Win, Loss or Draw. Let's take a look of Gwen lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Gwen.
Conclusion
Analyze the available data and learn how to beat Gwen. To master Gwen take also a look on Gwen builds and runes for Gwen. Good luck, Summoner!