Hi nightrunner19,
This post is similar to the one that you posted about the Quant section. Many of the same issues apply.
SC questions require a combination of knowledge (grammar and idiom rules) and pattern-matching skills (knowing the typical 'style' of GMAT SCs, the patterns in the wrong answers, etc.). If you're committed to learning that knowledge and building up your pattern-matching skills, then improving in SC shouldn't be too difficult, although it might take some time.
The Diagnostic Test in the OG is NOT a great way to assess your readiness to face the Official GMAT. For a far more realistic assessment, you should plan to take a FULL-LENGTH CAT (you can download 2 for free from
www.mba.com).
Many Test Takers spend 3 months (or more) on their studies to hit their 'peak' scores, so you shouldn't get too upset by any early practice CAT results. Training to score at a high level on the GMAT takes time.
All that having been said, it's important to define your goals and timeline, so you can properly plan out your studies:
1) What is your goal score?
2) When are you planning to apply to Business School?
3) Do you know what Schools you plan to apply to?
GMAT assassins aren't born, they're made,
Rich