Hello aspirant..

Actually it carry from person to person..but my suggestion will be 

If u have ample amount of time ...you should go through the NCERT books for Maths portion

High School English by Wren &Martin  for the English portion

Monoroma Yearbook for the GAT portion

But if u have less time in your time u can go through the complete package of (math+gat+gk+previous yr ques) I would recommend ArihantPathfinder..

Lastly you should brush up your ability by following the previous year questions of NDA 

Hii,

Union public service Commission conducts NDA exam twice a year.I suggest you to follow these books for better NDA preparation :

• Pathfinder for NDA and NA
• Chapterwise sectionwise solved papers NDA and NA
• Mathematics for NDA and NA by R.S Agarwal
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