You should go for M.Sc. (in any field that you want to pursue). This is the best option after completing your B.Sc.

To get admission in M.Sc. course, you have to first appear in an entrance exam. The most popular entrance exam is IIT JAM (Joint Admission test for M.Sc.).

Below are the best entrance exams other than IIT JAM through which you can get admission to MSc course.

National Entrance Screening Test (NEST)

MCAER CET

GSAT (GITAM Science Admission Test)

OUAT Entrance Exam