In this article, I will show you an easier method that you can do by yourself while keeping the money in your pocket. In addition, the few tools you need for the job are an investment, as you can use them anytime an issue occurs to the walls.
Tools for drywall repair

First on your list should be a cutter or an utility knife. You need the cutter to clean the holes and to give them a more common shape.
Then, you need putty knifes of various sizes. If you had to buy only one, then I recommend you to choose the 6" wide one. It is an excellent compromise and it should help you to fix almost any size of holes.
Last but not least, you need a good sander so you can smooth the putty before painting the wall. You need to use several grits of sandpaper so that you smooth the patched surface until it gets super fine. With these tools in your bag, you will be the carefree homeowner, as you can really repair any hole in the wall that might accidentally appear.