Get
-Kaplan Book
-DAT Destroyer
-Top Score
-Orgo Text Book
-Bio Text book
Id say first get your hands either on the Kaplan white book or blue book. Tear that up once (or twice if you have the time) and then start up on destroyer. Dont take destroyer as a test but as a learning tool. Any concept that is not clear check on your text books for a more detailed explanation. For Gen Chem you shouldnt need a text book since everything you need should be in Kap and Destroyer. After you have covered destroyer two or three times, start taking prep tests using Top Score.
Try to find other Practice tests such as Kaplans subject tests or Kaplans Full lenght. You could get achiever but I dont concider it a very good study source, others differ in this oppinion. Good luck and hope that was helpful!