jarvan iv is a very good ganker. Once you have at least half the build up you can start the ganks much easier because you would be just as good as a tank. to start off i would personally open up with your ultimate, put your flag predicting where they might go, once your ultimate is down then use dragon strike to disable them for a while, slow them and use your flash if you need to catch up to them, also use flash if needed to escape. a lot of the time when people have flash they use it to get out of your ultimate i feel that it takes to long for your ultimate to go down when you press R, you should just flash out with them and chase for the kill.


you should start off by playing safe try to harass as much as you can when u get the chance to, combine your demacian standard with your dragon strike as much as possible, later on in the game once you have got your phage you should be able to start ganking hard onto people, by then you should have quite alot kills.
you should be fine if you try to play safe at the start and after level 6 you can start going in for kills and go all Rambo on them.

hope you like my build Rate it and let me know if there is anymore information you would like to know about Jarvan and the build, i am always happy to improve :)