Well, I'm not in graduate school, but when my wife was applying, she knew she would have to take the GRE, so I bought her a copy of Verbal Advantage. I think I paid about $200-250 for it (they were running a special at the time), but it helped tremendously. She had taken the GRE once before, and her score after using it was about 100 points higher. That's a really big difference. I think it's worth it in the long run. I've seen it many times on Ebay in the $150-200 range. She used the Complete Edition, which is all ten levels. You can also buy the two Success Editions, each one of which is half of the Complete Edition, but it's cheaper to buy the Complete instead of the two separate halves.