I am thinking of slotting the nock end of my arrows and glueing a reinforcement into the slot. I am unsure of what material to use. Any advice or experience is appreciated .

Antler, bone, phenolic, or any hardwood will work.

Buffalo horn looks real nice too.

Just about anything will work. I like the look of contrasting wood.  

Of course, you can just wrap them, too.  

Any hardwood.  Just make sure your string groove is perpendicular to the arrows grain and the string falls on the face of the growth ring of your reinforcement shim.  Raptor Archery has a good demo video on the website.