There are two ways to prepare GK, one for scoring high and obviously its time consuming as well; may take upto 1 month, second method is to secure passing marks and may be prepared in 10 days. For both you have to buy PPSC Model Papers by Advance Publishers. If you want to go with first method then cover the whole book thoroughly and revise it atleast twice, the book contains almost 210 past papers. The second method is to only cover past papers of 2017,2018,2019 and 2020.