When should i apply??

Hi everyone,

I have a question regarding application for Canadian PR.
I am just about to graduate from a canadian institution.i am doing a 3-yr IT diploma from a toronto community college.I also have a job offer so that i can start working on a post-graduate work permit (no hrdc confirmation reqd). At the moment, i do not have any work experience in I.T. (my field of study).
I do have an hrdc arranged employment to support my application for PR.Assuming i can get a band of at least 7 next month in my IELTS exam, and finishing my diploma, i would surpass the 67 points....but still no work experience.

Question: Should I apply for PR after starting my job on the post-graduate work permit or should i wait until i have finished working one year??
CHC Islamabad's processing time for skilled workers with hrdc confirmed arranged employment is 12 months (thats what it says on their website).

Any replies would be appreciated.
Thanks.