The biggest misconception most have is that you can just decide you want to freelance and then do it successfully. That's most often not the case. Unless the skills you provide are something tangible like auto-repair or landscaping.
Conceptual services such as web dev and design require a track record of success and a proven ability to complete projects. There's just way too much competition to just jump in and be successful.
No one just "starts freelancing". No one. I've never come across a single successful freelancer who just learned something, then started surviving freelancing on that full time. Everyone works a regular job while building freelancing ventures to a point where they can survive.
You start the same way everyone starts. You learn the skills. Then you get a job using those skills preferably. If not, then any job. While you work that job you market and seek out those in need of the skills you want to use.
I've never used any "freelance websites" and preferred to make actual business connections. I worked my local market, finding businesses or individuals that needed my services. I networked with small business that didn't provide my services, but had a client based that could use them... so I could be a referral for them if someone asked them to do something they didn't do, but I did. There may be no "freelance market" where you are, but I'd wager that there are business or individuals who could use your services if they knew how to contact you. Face it, in today's world almost every successful business needs web dev or design. Every one. (well, I've never been to Brazil so maybe it's different there.)
You start with small, inconsequential, clients and projects that don't make a lot of money and don't give you a great deal to show afterwords.
You continue this until you have a portfolio of decent projects which you can show off to gain better projects. You work on those better projects. All while still working that job, whatever it is.
Wash, rinse, repeat.
You do this as long as it takes to build a stable of good clients that seem to always have work for you. And while doing this you save money. You save enough so that you can live, without income for at least 6 months or a year.
Then, and only then, do you take the leap to working freelance full time.
There's no shortcut or miraculous formula to working on a freelance basis. You have to prove your skills first and build a stable of clients. Otherwise you will just be spending more time looking for work than actually earning an income.