Hello,

The level of questions for PO in banking exams are comparatively higher  than that of clerk/assistant for that matter, also there is no interview in case of clerical exams, first and the foremost thing for any aspirant should be to be well acquainted with the paper pattern, questions come from sections like quantitative aptitude for which you can go for RK Agarwal's book for Quantitative Aptitude for Competitive Exam. if your basics isn't strong then go through NCERTs first for conceptual understanding, you can also refer to books like M Tyra's Quicker Maths or Arihant's Objective Mathematics, for PO as I said the level is higher in that case you can refer to management books by Arun Sharma or Sarvesh Verma.   for reasoning you can go for RK Agarwal's Verbal and Non-Verbal Reasoning or MK Pandey's Analytical Reasoning, for english you need to build your base strong on grammar then only you can effectively attempt questions from error detections. word swap, fillers, cloze test etc as all these test your understanding of subject-verb agreement, tenses, prepositions etc hence a strong hold on grammar is very necessary, you can refer wren and martin book on grammar, norman lewis's word power made easy is very good for vocabulary, also reading newspaper such as The Hindu on a regular basis will help in reading comprehension, gaining insights in terms of general awareness and also in recent times many of the RCs were taken directly from The Hindu, hence going through newspaper everyday serves a lot of purpose, you can also go through one business newspaper such as The Economic Times/The Business Insider/Mint etc,  general awareness is mostly focused on banking and economics, hence if you're applying for PO then this will also help in interview process as you'll be asked questions from these areas.

Remember that practice is the key to success in banking exams, speed with precision matter a lot here, there are many freely available mock paper pertaining to all the sections in various competitive exam sites(for banking specially), make use of them, this will help you in understanding how well prepared you are and if there remains area of improvement, apply test series before the exam as this is important to make yourself acquaint with the pattern of exam that is to be conducted in online mode, you have to make a routine for covering all these subjects, and accordingly assign number of hours to each subject, understand the concepts first, and practice on a regular basis, there are many YouTube channels as well where if you're stuck in any concept, then you can grasp understanding for the same, today with internet everything is accessible, but make sure to keep your resources limited, in an exam of this magnitude it's important that you have single-minded focus, dedication and perseverance to succeed.