What is advisable?Should I book flight tickets Before or After getting SDS visa?

Depends on airline's cancellation fee & policy. It'd be better to get a Qatar airlines ticket now because their cancellation fee is only 70$ but the prices would definitely go up more than that as the time goes.

Prarthana Khurana It's best to book a ticket which is refundable and Reschedulable one if you are willing to book before getting visa...

Apply for transit visa for USA, that route always remain cheaper to canada.

Rehman Sk I'm trying to book refundable flight too but fares are too high