Great post, Ceilidh! One thing I'd add: progress on the GMAT isn't linear! It's much harder to get from 650 to 700 than it is to get from 500 to 650. I tell students this a lot, but there's a perfect illustration in the news this week - Bitcoin! Everyone's heard about the unfathomable price spike of Bitcoin, probably in articles accompanied by charts like this:
Wow! This thing was just muddling along for years before skyrocketing almost overnight, huh? But what if we look at it somewhat differently, with a
log scale:
Looks a bit different now, doesn't it? Yes, Bitcoin has more or less quadrupled over the past four years ... but it more or less centupled (look it up, and have smelling salts handy) from 2012 to 2014.
Your GMAT progress will go much the same way: if you've got talent, a great work ethic, and the right materials, you'll make quite a bit of progress at first because points in the middle of the curve are cheap. The closer you get to the top, though, the dearer those points become, since you have to take them from your most talented competitors, the people in the 85th, 90th, 95th, and ultimately 99th percentiles. Don't get too discouraged if you find that 10 or 20 point gains are that much more grueling the further you've climbed.