Increasing V score by 15 points in 1 month is like climbing a mountain. V19 means you lack basic skills. You need to pump in at least 60 days with intensive effort on verbal section to reach your target score. I'd recommend first pick 'Wren N Martin' right away and brush up your grammar skills first. Thereafter, you can pick either Manhattan Verbal Strategy guides(SC, CR and RC) or Powerscore Bible set. After you are done with the concepts, start solving questions from OG on regular basis and learn from each answer choice (irrespective, whether you got a particular question correct or incorrect). You can pick OG VR thereafter when you run out of questions.
Hope it helps

You need to devise a section wise plan and then attack it. Start with the section you're most comfortable with, make some improvements in it and then move onto next. For SC, you can try out Manhattan GMAT or eGMAT. For CR, powerscore is the best. RC is purely about practice and reviewing mistakes you're making.
Review all the mistakes in great depth and try avoiding them consciously every time you attempt questions. Slowly you'll see the improvements and then take the full length tests to master timing strategies.