Personally, I found the MGMAT SC
book TOO convoluted for my liking - yes, their strategies are all-encompassing, but a bit overwhelming as well. But I'd recommend reading through the chapters first and doing their exercises first. Then, use the MGMAT OG Tracker and do all the OG problems and see where your hit rate is good/bad and go back and review those parts again. Personally, I had issues with parallelism when there'd be, say, two clauses of parallelism and I'd always pick an answer that went with the broader one, but the right answer would be the one that is parallel to the closest word. Simple things like that.