You actually are trying to do one of the hardest animation tasks there is.

Like lip sync (which is at least as hard) the human brain has a very fixed idea of what a "natural" walk looks like and is fairly unforgiving of what it sees.
I suggest you do a search of the forum on "walk." There are several techniques described here - from a simple, three-pose approach to an arrow-controlled walk using the methods associated with the hebuilder/shebuilder objects. And please post what you find works best for you.