First off look into the community guide, then the question guide and then of course the video thread (all under Jax). ALOT of good info and tips. Get the corner and mid screen kombos down, Jax doesn't fair well to zonners since he can't really zone back or teleport. So its crucial that you get down his highest damaging kombos and variations. Going against characters like Reptile, Kenshi and Noob...your going to have to make each hit count because they'll quickly switch up and zone you the entire game for that W.
Don't be afraid to use us for help or a source for new information! Alot of Jax players come and go and don't really use us as a source like you'll find in the other character threads. We can help you get over the basics with him pretty quickly