For starting, I would just go online somewhere and buy a strop and some compound. I would not get too wrapped up in details, colors, and grades of leather. I say this because, you may damage your strop during the learning curve...or you will likely decide at some point that you want more, or smaller, or larger strops.
After you have one and learn to use it, you will be better able to figure out what you really want.
Personally, I like a long wide strop made from hard leather mounted to a hard surface. I get great results and a buddy made most of my strops for me out of some hobby store leather, and some spare simulated granite countertop material he had left over from a job. I use several loaded with various grit sizes of diamonds (works best for high wear resistant steels).