Any links to articles you guys suggest me to read? Thank you for your replies and advices!
You're in the #1 place: NamePros.
I also think Michael Cyger does a really good job with his videos on
DomainSherpa.com.
What do you guys thinks it's better, thinking my own domain or purchasing already existing one at low cost? Because I have great domain ideas that are available
I use a mix of both strategies and both have worked for me. However, a ton of research and now, experience, informs what I buy these days. And even today, I am dropping a number of names that I thought were great ideas when I bought them a year ago

And I am profitable.
You have to be careful especially when starting out, because you can go on a real tear registering tons of names that you think are gold but turn out to be un-sellable.
Last thing: domaining is not easy and it is not, in my experience,
passive. Like some others have said it takes a ton of work, research, watching auctions, even a ton of administrative work if/when you have built up to hundreds or thousands of names in inventory. And, you probably need to have an above average intelligence and a lasting passion for this niche market we call
Domaining in order to "live from it."