shock educated me a while back on the best layout for mk w/ most keyboards. wasd are the directionals, and then if you've got the 6 button layout over your directional keys (home delete end page up page down etc) you use those as the the button config. These are the best keys to use for the buttons since they're the closest to real switches, open/close style. Some keyboards won't let you charge buttons on on other keys, so no bicycle kick, ground pound, or sai, h. smoke, etc. (I used to like to bind hp hk blk run and back all to the same key so I could just hold that down)
If your keyboard doesn't have the charge problem and you don't mind using your left hand for the buttons, asdzxc is great because you also have easy access to shift and space for double binds.
With all that said, fuck the keyboard, buy/build an arcade controller!