May I suggest before you buy any other stones watch a few videos on how to sharpen. There are some on this site that are quite good and You Tube has tons. Practice is the key and polishing or stropping the blade is just as important as getting it sharp. Learning proper blade angle is key to getting it sharp. I use Japanese water stones and usually only need to strop to keep an edge but that also has a lot to do with what you are sharpening, the metal its made of and how you use it. Lots of ways to accomplish sharpening and each tool you sharpen will be different.
Dave