As for the reading, I strongly recommend the Ann's reading method, it is really helpful. Follow the steps and you would find the answer finally. As for the math, I only study the jj. While I think the og is a good material for you. But as I mentioned, always think it by yourself before you get the answer, you would definitely find the way out.
SC: PP, Manhattan=>記得grammar一定要融會貫通,不是只有單記解釋, 這樣你到後來還是會犯同一個錯誤 By the way, when I found something I donn't know, I would search Manhattan/beatMBA.com to see if there is Ron's explantion. Ron is the one who got 800 before and he knows about every classcial grammar in terms of GMAT's preferences.
CR: this is the most challenge one. I used OG, PP1 to prepare it. And again, if I do not know the explantions from the book, I will find Ron's answers again. And you could find the articles of SDCAR2000(not sure if I spelt it right) in the CR section in Chasedream. He/she wrote a series of excellent introductions about the CR. Study it hard, I think it would help you a lot.
RC: This is the part that I prepare least. I only do it in GWD and PP. To start this section, I think you could try the Ann's reading method first. Grab the idea and the implication from each paragraph, you would find RC is not a monster anymore.
Remember, never give up before you try it! You would find your way out finally.