No, there is no particular order to the questions at all (at least none that would be of use to students--certain groups of questions tend to appear together because they appeared in that order in previous editions of the
OG, but that's all I can see).
Yeah, most people agree that the math in the
OG is not representative of that they will see on the real GMAT if they're scoring high on the math, so you might want to seek out sources of harder math questions.
Kaplan offers a very good introduction to the GMAT, but to do your best, you'll need to keep studying and practicing.
