Hey.

English - For Vocabulary you can refer the Word Power Made Easy. You will come across various words while reading the newspaper too, prepare a list, go through them regularly and try to use them in sentences. You should read the Editorial section of the Hindu for your Reading as well as Vocabulary section of CLAT.

For grammar you can use the Wren & Martin.

This is as per the requirement of thr CLAT Syllabus other than that you should start reading newpapers, English Novels, Movies etc for a better grip in the language which will develop gradually.

Mathematics - For Quantitative aptitude by RS Aggarwal. Other than that previous year question papers and Arihant/ Universal guide migh help too. The mathematics syllabus is easy as it includes elementary level maths. So working upon it as mentioned above will be sufficient.

Best of luck!