The speaking skill is the most imporant of all of them. Let me explain to you, people who now a language are referred to as “speakers” of that language ; when you speak you are using the other skills because the other ones give us tools to show an idea.
If you want,you can see this interesting video about commun mistakes that people make at the moment of pronounce some brands.
Here in the next link, you can find a great way to practice some expressions that are useful at the moment of speaking.
The Language Skills 