Short answer: Prepare the common sections once and add exam-specific practice for the pattern differences.
Common core
Quantitative ability, verbal ability and reasoning appear across these exams, so a common base serves them all.
Exam-specific practice
Check the latest pattern of each exam and practise accordingly, especially for XAT-type decision-making sections.
Cost control
Buy one good book per section and use second hand copies when the edition is recent.
Frequently asked questions
Can one set of books cover several MBA exams?
Largely yes for common sections, with extra practice for pattern differences.
Where do I check the latest pattern?
On the official website of each exam.