There are two options I can suggest to you based on the little experience I have.
Option 1)
Self StudySelf Study strategy can be different for different people. For example here's what I have been doing for past few days, preparing mainly for SC:
Day 1 :
Theory: Complete Chapter 1, 2 (Meaning) from
MGMAT SC Guide
Practice for the relevant theory : Meaning based questions 13th Edition: 10, 14, 20, 21, 25, 31, 39, 49, 58, 94, 96,135.
Meaning based questions Verbal Review: 3, 18, 22, 36, 54, 72
Day 2 :Theory : Complete Chapter 3 (Subject-Verb Agreement) from
MGMAT SC Guide
Practice for the relevant theory : Subject-Verb Agreement Questions 13th Edition: 3, 6, 7, 16, 30, 45, 61, 67, 70, 81, 88, 103, 129, 133, 140, D41, D43
Subject-Verb Agreement Questions Verbal Review: 10, 11, 14, 20, 34, 35, 65, 101
and so on...
I am targeting SC first because I believe it will help me to comprehend CR arguments better. And improving CR will consequently improve RC. This is just my assumption. I don't know what works for others.
I make the plans and self assignment such as above in advance for the next day.
Right now I am at chapter 9th and my overall accuracy is exactly 89.27% in SC. How am i so sure about the accuracy?
I have maintained an
error log of each and every OG SC problem I have solved. Its like the most common thing that experts recommend.
I solve each and every OG problem under timed condition. Initially I used to allot 1 min 30 sec for every SC question, but now I have started restricting it to 1 min 15 sec. And it includes the time spent for some petty things such as turning the pages, locating the problem number etc.
Option 2)
Prep CourseYou can choose from loads of prep courses that suit your need. Try to research properly about them before spending money. One of the options is to scan through reviews here:
https://gmatclub.com/reviews/?fl=menuAlso make full use of the ones that offer free trial. What's there to lose?
If you have some time, try to browse the forums as long as you can. There are loads of success stories here. I have subscribed to gmatclub newsletter and I get links to new success stories every now and then. They inspire you, and give you lots of options.
Good Luck preparing.