This is what a typical pre-med path would look like for those who want to be able to attend medical school RIGHT after they graduate. That is, if you were to gradute in Spring 2019 and want to attend medical school the Fall 2019 cycle, then that means you would have applied by Spring 2018 because the application is a year long process. You would need to complete the MCAT between your 3rd and 4th year as an undergraduate. If you are not ready to take the MCAT, DO NOT TAKE THE MCAT! It is best for you to complete the prerequisites before taking it. If you do plan to take a gap year, things would still be the same; instead, you just apply the year that you are going to graduate. So if you plan to graduate Spring 2019 then you would apply Spring 2019 for the Fall 2020 cycle.
General Timeline of the Application Process for Medical School
This is the general path of medical school. Depending on your speciality, residency may be longer than 2 years. This is what you would expect to be doing for your medical career path.
AAMC Official Timeline to Medical School