How to counter Gangplank
Let us take a look on how to beat Gangplank. We will look at champions who are strong against Gangplank and who are weak against Gangplank. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Top champion who counters Gangplank. You can already win in champion select with the right counters for Gangplank. If you want to know how to counter Gangplank then you need to take into account the best picks vs Gangplank and the worst picks vs Gangplank. This Gangplank counter data is based on matches played by Pros on patch 14.9 and previous ones. It is important to see whether Pros counter picked Gangplank or whether they played as Gangplank.
Champions used by Pros to counter pick Gangplank
Looking at the matches from Pros (see table Pros counter picked Gangplank) we can see that they picked 
Rumble most often to counter pick Gangplank. The matchup Rumble vs Gangplank occured 8 times. Gangplank has 6 wins and 2 losses in this matchup. Learn how to counter pick Rumble to get another perspective on the data.
Lane outcome for Gangplank
When looking at Gangplank 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 Gangplank. The lane outcome of Gangplank consists of three outcomes: Win, Loss or Draw. Let's take a look of Gangplank 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 Gangplank.
Conclusion
Analyze the available data and learn how to beat Gangplank. To master Gangplank take also a look on Gangplank builds and runes for Gangplank. Good luck, Summoner!