Canada

Try getting anything above 80% as you need to have good academic scores. So aim for 85-90% as it is going to strengthen your case. Even if you get a little below 80%, try scoring really high in your SAT exam. Since both these scores are taken together, you need to focus on both.

Hi Mehtab, why do you want to do a diploma after BBA? You must look for PG Diploma or Graduate Certificates. Either ways, yes you can pursue a PG level course in Marketing if it suits your career plans. Seneca is a popular college and also offer co-op education which is very helpful for students.

1.Computer Networking and Technical Support
2.Computer Programmer
3.Computer Programming and Analysis - (Optional Co-op)
4.Computer Systems Technology - (Optional Co-op)
These are list of good courses you can opt for. They all are available in Seneca college (Toronto)
You can check their website for more details.

Hi Bhaskar, have you taken your IELTS or TOEFL?

Yes, you can do it.

You can't get admission in a high ranked university but you can easily find a good course and apply for it in an average university. Look for a university in not very populated area

Dear Kenneth, few of the best universities I know of would be University of Miami, Columbia University, University of California-Los Angeles and University of Pennsylvania and University of Illinois at Chicago in USA. In Canada check the nursing schools of McGill University, University of Western, University of Alberta and University of Toronto. There are many more to the list. You must be giving the GRE to be admitted in US. Please visit the websites for admission requirements and other information.
Best Wishes

One year gap is fine as long as you can explain the reason behind it.