I don't think we can really suggest anything till we know about the strategy you used ? Would be better if you can give more details about your approach otherwise I don't think we can give you anything better than generic replies,which might not even work for you.
I use the Manhattan SC to review my SC questions ( I am in ESL country). besides, I usually do some CR and RC questions from the PREP. but I find out that my weaknesses are SC and CR, and my RC is just so-so.
I want to find out a way to improve my SC and CR. thank you !