Ok, you have your working visa & passport. But please
check with Qatar Embassy in your country (if there is) if certification of these docs is not necessary before buying your ticket.

In my country, the printed Qatar visa together with the
original passport have to be sent to Qatar Embassy for certification and processing time is 5-7 days. When we receive back our travel docs, that's the time to buy the ticket or we just estimate processing time and buy the
ticket right away.