My main prep for SC was the
Manhattan GMAT. After that it was reading the official explanations in the OG for each problem. You'll eventually pick up some of the GMAT tricks (that are never written, even in this forum) like
The application of pesticied and irrigation were costly...
This is a common mistake that I never found an explanation for but is always listed as "unclear" in the OG. It is "unclear" since 'application of' refers to pesticides and irrigation and you don't apply irrigation.
Anyway I learned to be fearful of the "of + noun and noun" construction just by reading the OG.
I would recommend doing the OG first because you want to know why you are getting them wrong and it gives official answers/explanations. You don't know where the 1000 problems are from and I know some of the answers in the 1000s are wrong because the answer is in the OG is different. Plus although a lot of people here are pure genious, you never know which explanation is actually correct so I liked to work with OA and OE.