Hi bro,
Thanks for sharing your experience, I have a question for you would really appreciate if you can answer:
You should be very careful dredging up old information - alijumani and mesumrizvi posted in 2016, and program rules have changed a few times since then, so their experience does not necessarily help you now, and may mislead you.
See the last paragraph, "Waiting for a decision" for current rules.
https://www.canada.ca/en/immigration-refugees-citizenship/services/study-canada/work/after-graduation/eligibility.html
I graduated on 20th April, 2017 and started working full-time from 1st May, 2017 but I applied for my PGWP on 19th July, 2017 & received it on 1sr November 2017. Should I include my work experience towards CEC from 1st May or counting it from 19th July would be better ?
You became eligible to work on the date you submitted your PGWP application, so you can count your work experience from 19 July 2017.
HOWEVER, also note that when you graduated, you were no longer eligible to work under your study permit, because you had not yet applied for your PGWP. In effect, your work experience from May 1 - July 18 was unauthorized.
Also, is it a good sign to show full-time experience gained before applying for PGWP ?
Since it was unauthorized (and therefore illegal), I would say no, it is not a good sign. Unless you are referring to working while a student (not eligible) or before you became a student (eligible, if classified as skilled). But the post-graduation/pre-PGWP application work - no, not a good sign.