My pleasure walkahead bro !

"or would it be easier first to apply PR for my parents and after they got their PR then apply for my siblings?"

If your siblings are unmarried and under 21 yrs. of age then it would be much quicker if your parents apply for them after they get their GC. It's spouse and children of permanent resident; category F2A.

If your siblings are unmarried but 21 yrs. of age or older then it's F2B (Unmarried Sons and Daughters (21 years of age or older of permanent residents): As you can see on the table they are currently processing application filed on or before 01 APR 05 in this category.

Married sons and daughters of citizens fall under category 3rd.