DMT has a combo pack of double sided stones extra course through fine it’s reasonably priced. I added a much larger xx fine because I have a lot of woodworking tools to keep sharp but the little combo kit is good enough for non woodworking applications.
A lot of companies want to sell a lot of crap when sharpening a knife just takes a little practice and some cheap tools. There's guys spending thousands of dollars on sharpening solutions, when all you really need is less than $20.