How many programs should I apply for
It depends... The better your profile matches the specialty, the fewer programs you need. It is also very important to find out upfront what a program requires from its applicants. Usually each program has specific requirements for USMLE scores, attempts, year of graduation, ECFMG certification, etc. In general, Application to Interview ratio varies from 5 to 20. In other words, if your profile is on a low part of the scale, you should expect about 5 invitations for 100 applications.