BITSAT Eligibility

Start from basics, first of fall clear your basic concepts and work on the subject you have knowledge and make that concepts strong, if you want to clear the exam in least amount of time it's better to strong the concept you already have a little bit of knowledge, rather than hoping on new concept. And manage time also practice questions with timer !
Practice a lot of questions, Revise through questions, Do previous year question as much as you can this will help you to understand the level of exam and your weak and strong points. For Chemistry totally focus on ncert, complete it plus do pyq. For Maths and Physics first clear your basics through ncert, plus do a question booklet and ofcourse pyq. If you do these with consistency and sincerity you will make it !
You specifically don't need any coaching there are certain platform on which you can study completely free they will guide you ! Or you can take subscriptions to some online platforms but you will get every material and help on YouTube and on various platforms. I cleared JEE without coaching, it's all about your hardwark, consistency and patience !
Hoe this helps !
Thankyou!