Dear Aspirant,

NO NCERT alone is not sufficient for JEE Mains and JEE Advanced. NCERT might help build up basic concepts but to gain problem solving skills for questions of difficulty level asked in JEE Mains and Advanced some standard reference books might help. NCERT might help somewhat  in JEE Mains but for Advanced it won't help as questions asked in JEE Advanced are highly conceptual and require good amount of problem solving skills,approach.

Some standard books that all IIT-JEE aspirants use can be found here-

https://engineering.careers360.com/articles/best-books-for-jee-advanced

https://engineering.careers360.com/articles/jee-main-important-topics-books

Now coming to marks required,

See the exam pattern and total marks for JEE Advanced changes every year and students come to know about it on exam day only.Now it has been observed that scoring 30-40% of total marks of JEE Advanced paper 1 & paper 2 helps securing seat in IITs.Now considering sc category this much marks would surely help to get a good branch in top IITs.

check this-

https://engineering.careers360.com/articles/jee-advanced-cutoff#JEE-Advanced-Cutoff-for-Top-Branches-in-IITs