First, avoid Amazon. All the stones on there are scams, if you contact the manufacturer you'll see that these stones are less than a dollar in bulk.

I sharpen tons of knives and tools, so I use around 5 or 6 stones, but if you are looking just to sharpen your knives, you only need 2, and a strop.

I'd say most people only need a 1000 grit stone, especially if they have a strop. I've been using a naniwa lobster for a while. Even though the aluminum oxide abrasive is not very aggressive, and slow on very hard steels, it leaves a very keen edge. After some stropping you will have a razor sharp edge if done correctly.

Of course there are many other options for good stones, shapton's korumaku series, shapton's glass series, naniwa chosera/professional series, king (in general).

Aside from water stones, diamonds are also popular. In my personal, unpopular, opinion, they cut so efficiently that the feedback is lacking and it's difficult to get a crisp edge off the stone. They also don't like abuse and can be ruined with aggressive use.

For the strop, you don't need anything fancy. You also don't need compound either, though I usually use natural stone powder.