There's an easy answer to this question: everyone's advice has been wrong!

It makes no sense to start with either topic first. You should study quant and verbal concurrently. There's a common misconception that we learn best from massed practice (e.g. doing a whole lot of one thing), when precisely the opposite is true. We learn best by developing in several different ways at once. Just as you wouldn't get in shape by exercising your biceps for a month before moving on to your abs, you don't want to focus on just one broad area or the other.
So . . . get yourself some good materials and start in several places at once. If you are a non-native speaker and need more help with the verbal, start on SC right away, because you will need lots of time to build up all the rules and strategies that will get you through. You can also start to familiarize yourself with CR and RC. I'd recommend RC a bit over CR, because learning to read effectively for the test may help you on CR as well.
On the quant side, take an initial practice test (if you haven't already) and use that to determine the most important focus areas. If you are going to work through a full curriculum (such as the
MGMAT books), you can certainly start from the beginning. If you're already doing really well in quant, you might jump straight into addressing your weaknesses or pushing yourself on the more challenging problems. (We have an Advanced GMAT Quant book for people already hitting 70%+ on Quant.)
Wherever you decide to start, don't get stuck in a rut doing one thing to the exclusion of all else. That will give you the
feeling of progress without the actual
result, and I'm guessing it's the result that you care about.