The OG is certainly an important study tool--that's where you get real GMAT problems to practice on. I think people severely understate the difficulty of the material in there. Many of the problems are quite challenging if you hold yourself to strict time limits. The problem with the OG is that it isn't a *teaching* tool. If you don't already have mastery of the underlying content, you're not going to gain it by doing OG problems and reading the explanations.
So sure, I recommend that you work through our strategy guides, or *someone's,* to make sure you have all the necessary skills in place.