CA Foundation covers most of your class 12 concepts and basics . In order to prepare for CA foundation you need to religiously follow the ICAI material as all the questions are from the ICAI module itself. Along with that solve the past year papers , RTP and MTP for atleast the last four attempts and you will ace this exam. If I give you a brief idea about the subject wise strategy then for accounts conceptual clarity and practice is the key. For Law go through the provisions as well as the examples. The case studies that are asked in the exam are from the examples itself. For economics and BCK just read the chapters 4-5 times and you'll be done as the paper is MCQ based . For Maths again conceptual clarity is a must along with practice in order to gain speed for solving the MCQ.

All the very best for your preparation!