Yes, the walkcycle should start and end in the same position and you should achieve the starting position in 16 frames.
Doing it in such a low number of frames forces you to keep the keyframes and timing clean. It’s lot less work and the rest will be interpolated quite acceptable.
I’m not very experienced with animation either. This is my first walkcycle, which I’ve done a couple of months ago. It’s still pretty rough, I haven’t had time to work on it since, but there are some points visible, which you should probably follow, too
don’t let the feet slide
keep the count of keyframes low
open the knees
try to do a bounce
I’m sure better animators on this forum than me, will be able to extend this list
Try giving it’s back some play, too. Its good, overall, but anything that adds to the conception of walking. rotating shoulders, outturned feet on the step, etc. also remember that all actions in an average walk cycle are curves. arms swing like pendelums. rotate the spine, too to accentuate the step and arm swing.