zer2727 welcome to Gmat Club. Since you are planning to appear in may next year. you got pretty much time to convert 300 to 700. Don't strain much.
You Should start with the section you are facing more problem. Be it SC, CR, DS, PS pick any.
First you have to cover your basics and manhattan guides are best for the purpose.
After completing Manhattan you can practice from OG 20/21 it will be your choice.
The additional book material and study plan information you can gather from the following link:
https://gmatclub.com/forum/gmat-study-p ... l#p1680625Plus if you face any problem while solving questions, use search bar here on Gmat Club, you will automatically find link of that question, But if there by any chance, you don't find it here. Post it while keeping GC Posting rules in mind:
https://gmatclub.com/forum/rules-for-po ... l#p1092822Do share your futher query, we all will be happy to help.