There is little hard to play with jax, but its one easy way to get kills and to not get killed :D
When u are going to attack a enemy u should use W, and then Q.
First of all u need to unlock Q so u can jump and attack, so runn back and do the same all the time.
Its a strategi and its not hard.
If you are going to jungle with jax, theres one thing u should now. use clarity and flash.
you most alsow use armor and health poision in the start (if jungling or not)
If you are playing against jax and ur another champin stay at turret and dont push hard. Jax is a good pusher and can easly kill u if your in mid of map. (bot or top / mid).
If your jax is getting 5 kills in less than 10 min you can buy many things and get little op with build in the start.
Be carefull if your jax in small lvl (online) to not jump on enemy when theyr recalling if you got little hp left. (if u would jump on him and Flash away).