I am planing to write a setting book, adapted for 5e rules, not this year, maybe not next one, but someday, and I'm asking for some advice, what should i do once i finish the setting book to make people play it? (apart from my friends obviously) should I look for a publisher?
You can look for a publisher but might have to self-publish. Start small. Write an outline or one-page synopsis and see if it resonates with gamers or even just your friends. Then, write up a 3 - 5 page treatment and see if that gets people talking. If it does, then you're on the right track and can go from there.