You're on the right track here. Only missing a couple of things.

In order to get your leading leg to be able to step forward, you actually need to move the entire body forward as well. When you walk, your whole body moves, not just your legs. In addition to moving forward, the torso will need to move down a bit as well to allow the feet to touch the ground.

The way you have your rig setup right now does not allow for easy animation. You should parent the IK handles to some form of control object -- the easiest thing to use is a null object. You should also parent the root of the skeleton (in your case, "joint1") to a control object. When you animate, you manipulate the control objects instead of the IK handles.

I've attached a slightly modified version of your file so you can see what I mean. In this file, I've keyed in a very basic step animation to illustrate my first point. I've also rebuilt your IK handles (you were missing on and something was acting weird), and I've used custom NURBS curves as control handles. Take a look at the file and let me know if you have any questions.