ask a teacher,i have to read and i have family, how do you planning to read the journal/book? how much time you spend to read? what book do you choose in biomedical science? especially microbiology and parasitology?
The more you read, more your knowledge become. So I do not think one can give a number. But if you think of selecting journal articles impact factor of that journal article is a good indicator of the quality. Higher the impact factor of the journal higher the quality.
The fastest way to increase knowledge in a certain subject is to teach that subject, if that is not available, the best way is to publish articles in that subject, not necessary innovations, reviews are good and acceptable.
In this way, the researcher forces himself to read extensively, concentrating on up-to-date articles.
The more you will read carefully the more you will know about the subject. Read good books and good articles which will certainly help you to enhance your knowledge. One must sleep at least 6 hours a day to keep mentally alert and physically fit.
Read papers, a lot of them. I'm only 14, and to gain the knowledge in neuroscience I have today, it all came down to my willingness to learn. If your truly passionate about your field and you read and learn as much as you can, then you will ultimately have a very good understanding of your topic.