For covering basic concepts and practising standard questions, NCERT and R. D Sharma is enough. But for BITSAT, you need more than just basic concepts. Speed is just as important as accuracy, so make sure to practice solving a number of problems within a given time limit. Practise and solve a lot of past year questions and question papers to get familiar with the pattern. After you have covered the syllabus, start with practising with a time clock and a fixed number of questions so as to improve your speed and accuracy. You can buy a test series of a good coaching institute for proper practice.
Hope this helps. Good luck.