Okay get the Collegeboard blue book, Direct Hits book, and an SAT book such as Barron's or Kaplan. For the Math I would suggest just learning all the concepts and practicing questions. For Writing there are guides online, I know there is 1 on Sparknotes, you can use that to study and practice your grammar rules. Then spend some time and memorize the vocab in direct hits, get both versions. I suggest you to do 1 practice test in the Blue book and then review all your answers after you learn all the stuff. The Barron's/Kaplan book is mainly used for additionally practice because it seems like you might need more questions. After practicing and learning the stuff, go back to the Blue book and take another test and carefully review each question. There are guides all over CC to help you out, good luck!