The whole problem you have so far is that none of the legs overlap like they do when you actually walk.
Think of walking as pushing yourself forward with your rear leg while your front leg hovers in the air until it finds a spot to push off of.
Thus, starting from standing position, a leg should go through the following:
Slight bend, raised
Sharper bend, raised slightly higher
Decrease bend, lower slightly
Remove bend, foot on ground
Then curve the leg backwards like an arc, compensate for any errors.