How do you make a custom footstep sound script?

Alright. I've been trying for weeks now to make a footstep sound script that plays a sound when you take a footstep. Problem is, all of the ones I have made have just been looping the same soundfile, making it out of sync, I can't find out how to make the sound play ONCE per time on of your feet touches the ground, and for it to play a sound out of 5 different in a folder of the same material, which means that i need the footsteps to be played depending on material your feet are touching. This seems hard and is hard. gyazo.com/3a71005fc817ffdeab4871346fea6a8c

A picture of the sound folders, all with slightly different walksounds for each material.

If you can help, that would be awesome.