I'm a citizen of India. I'm 22 years old and have a bachelor's degree. My sister and brother-in-law are U.S citizens and would like me to apply for a dependent or immigrant visa since my parents are retired and are unable to financially support me here in India. I would also like to study for my Master's Program in the U.S. and am currently giving my TOEFL and GRE exams.

Will I be eligible for either of the two visas?

If your sister can support you financially, then she can sponsor you a student visa but it would be very difficult because you're entitled to immigrant visa as well. The problem is if your sister sponsors immigrant visa for you, waiting period will be more than 15 years.