Hello, and welcome!
Here's my $0.02:
Verbal: Being above average in CR is important, because that part is hard to teach. RC levels can be elevated by challenging yourself with some professional-sounding material. Pick up The Economist
or The Wall Street Journal and read 2-3 articles a day. You're guaranteed to get faster and to absorb more within a month. In addition to that, buy the Official Guide (13th ed) and go through all of the practice problems. Your approach to SC can vary, depending on whether you are a native English speaker, and whether you have an understanding of the mechanics of language. Pick up the MGMAT books
and focus on Subject-Verb Agreement and Parallelism. That should boost your SC a fair deal.
Quant: I'm going to be honest - with a 31, you might need to go back and brush up on your fundamentals. Grab the Foundations of GMAT Math
, by Manhattan, or another similar book that can take you through some of the basics. Don't worry - it's nothing to be ashamed of. Plenty of folks forget all of their high school math and need to do some serious revision. Once you go through that book, it's very likely that you'll be beyond a 35, and you can then do the Official Guide's quant problems for practice.
A few tips that helped me on my way: it's great to have determination, but you need to channel it correctly. Doing x problems per day doesn't necessarily equate to success, even if x > 100. Your focus needs to be on why you got stuff wrong and how you can avoid similar errors on the real thing. There were days when I would go through 50 easy problems, make 5 simple mistakes and move on. Other days, I'd go through 20 difficult ones, make 5 errors, and spend 3 times as long on them. Think quality, not quantity.
That said, if you put in 150+ hours of focus and dedication, I would be very surprised if you didn't score more than 500. If your prep goes well, I can bank on you to score 600+. If you need some inspiration, have a poke around this forum and see the stories of some folks who made enormous GMAT strides (I'm talking from <500 to >700). Best of luck to you!