depending on what you want to spend there is no doubt that the accuracy of professional grade test kits produced by companies such as
Lamotte or
Hach are considerably more reliable. However, if cost is a factor your LFS should have a variety of hobby grade all in one test kits to suit your needs.
Do you know specifically what parameters you are interested in? I find the issue with all in one type kits is either you may pay for some parameters you are not overly interested in or they have most but are missing one or two parameters you are interested in. Furthermore, you are likely to run out of some reagents faster than others. Just some things to consider before you buy.
If you have any specific questions I am sure myself or other members would be more than happy to help you out.
-Ian