Take any book for EDS, I prepared from World Times book but my previous knowledge was also handy. Also do past papers of last 6-10 years, many questions do repeat! If you have science background, you can easily score above 70.
In current affairs, read dawn to keep yourself abreast of recent issues and then make a list of about 5-6 hottest national issues and 5-6 international ones. Search them on internet and gather various points of view. I gathered a lot of material on CPEC and National Action Plan and luckily they came (I even drew the map of CPEC). Key is to have the measure of things happening in the world now. For instance, recent escalation in tensions between India and Pakistan is a hot issue and it can be asked from different perspectives - is nuclear arsenal really a deterrent? Kashmir issue, and what role international community can play in its resolution. ISIS and Syria and Middle East. Is Middle East really a Shia-Sunni conflict or are there deeper motives at play? Energy crisis, poverty, education and terrorism are ever hot issues for Pakistan (unfortunately). Sustainable Development Goals are also important, especially in the context of failure of Pakistan to achieve Millennium Development Goals. Regarding climate change, Paris Accord is important. Also anti-muslim sentiments and Islamophobia is at rise in Europe and USA, what can Muslims do mitigate that feeling?
To be honest Current Affairs was easy in 2016 and it may not be the case this time around. I was also able to complete this paper; my writing is very slow and I couldn't complete papers of Pak Affairs, Public Administration, Computer Science and Physics. So if you can write some material and write it good enough, you can definitely get above average marks and that goes for all the subjects.
Anyways give current affairs at least 1-2 weeks worth of your time and like I said earlier gather some notes and references too!