If you are looking for a kit that comes with a filter, most starter kits come with everything included that is relatively cheap and easy to set up.
Here is a great kit that comes with a filter
5-gallon fish tank kit
A word of caution when purchasing a kit!
The filters provided typically are just enough filtration for the tank. As a general rule, I usually like to use a filter that is rated for a slightly larger tank than the tank I have.
As an example;
If I have a 10-gallon tank, I would prefer a filter rated for 20 gallons, which ensures the filter can handle the tank and provide a little more filtration.
The more filtration is better!