I use stones now, but when I was learning to sharpen my knives, I used a Lansky Sharpening Kit. I learned the angles and what the stones do from the kit, and bought some good stones from Japan.
For my American friends, don’t bother with the stones at Harbor Freight. That’s the one tool that I have found that is just going to cause more frustration trying to use it, rather than just buying a good one.
¼" to ½" is all most cats need. They are surprisingly flexible