You should be very smart when you begin preparations for any competitive examinations. Okk so I'll try to guide you as per your subjects. For English, you can use SP Bakshi Objective General English (Arihant) and RS AGGARWAL quick learning objective English book.

From improving your grammar skills you can refer to High school English grammar and composition by Wren and Martin.

For LEGAL APTITUDE, refer book by RK GUPTA.

For verbal and non verbal reasoning, go with RS AGGARWAL book it's really worthy. For Maths ie quantitative aptitude go with Rakesh Yadav.

BBA entrance exams generally covers following areas to study on:

Quantitative aptitude

General awareness

Reasoning

English

Best wishes. Thank-you.