I have no idea about your location in the world. Perhaps in your city university education is not a necessity. Perhaps in your region few people finish their primary education. But in that case, it means people in your area are not technically advanced.
When I review applications -- which I do frequently -- nearly every person has at least a bachelors degree. Some have links to a portfolio, many list their hobby projects.
You do not compete in a vacuum. If there are other people who look better on paper or on the job application your portfolio will never be looked at.
There are some people in the forum who live in regions where formal education is less important, or who did not get college degrees. If you happen to live in one of those places where college or university studies are not required you should still finish your regular school education.
I was thinking in leaving school, and then read books, forums and take classes of digital arts online, with books and forums like this, with the internet maybe i can learn more, and learn what i really want to, what is going to actually be useful in my future.
That is a terrible idea. Stay in school. Get the most education you reasonably are able.
Stay in school AND read books AND read forums AND read technical papers. If possible for you in your region, also go to university or college studies.
While you are reading material online and in books, talk to your school teachers and ask them to help explain topics as you encounter them.
Take advantage of the opportunity you have been given.