You want sharpening stones that will be useful for the majority of your edges now, and that will remain useful as you expand both your tools and your sharpening toolkit in the future. Ending up with duplicate stones or ones that are no longer useful as you gain new knives or tools is a waste of money. The goal is to start with something that will stay with you as your needs develop.
Unfortunately, the arrays of modern whetstone can be bewildering to the inexperienced sharpeners that so often times many of them end up with a crap or wrong decision on stone type for their utensils. The most difficult to determine is whether the whetstone is fake or fabricated with low quality of materials. To avoid this you can only go for the reliable brand of a whetstone.
Practice holding the knife at a 20 degree angle. Most straight blades need to be sharpened at a 20 degree angle. To find the angle, hold the directly in front of you so it's straight up and down. This is 90 degrees. Tilt the knife halfway towards the table so it's at a 45 degree angle. Tilt the knife halfway again so it's about an inch (2.5 cm) above the table. This should be a 20 degree angle.
My first set of sharpening stones so I have nothing to compare them to. For $50, though, great price to get into the world of sharpening. Stones are great and easy to use. Was able to put hair shaving edges on knives. Took a couple of knives to feel comfortable and better with the process and how to sharpen, but the stones you get work great. Here's the secret though. Get the green leather stoping block as well. As great as the stone are, I have found that stroping the knife after the fact is what really brings out that razor edge. And after using the knife, stroping it again, will restore and keep it razor sharp. Hope you enjoy it as much as I am.