What were the immediate positive effects of Gutenberg's printing press?
The immediate positive effect of Gutenberg's printing press was that educational and religious texts became much more widely available in Europe (I will assume that this is a positive development).
Gutenberg published his first Bible in either 1455 or 1456. By the year 1500, there were more than one thousand printing presses using movable type in Europe. These presses were putting out large numbers of texts. By 1500, they had published between 8 and 10 million copies of about 40,000 different books. (All statistics here from Jackson Spielvogel's Western Civilization7th edition, page 355.)
This allowed the spread of knowledge and helped to create a more educated and literate public. This was the main immediate importance of Gutenberg's invention.