I had to raise my quant score and I mostly used the Manhattan Prep 5 lb book of GRE practice problems. It’s not expensive on amazon, it has tons of questions, and it has diagnostic tests so you can pinpoint what you need to work on. It took me from 60th percentile to 90th+. It didn’t “teach” the concepts so much but the repetition from doing so many problems made it easy to recognize the types of problems and the trick questions.
