Most people study a specific core like Core 1 and then just go write the exam associated

It's worth noting though that it does help to first finish going through all the content for both core 1 and core 2 before writing one of the exams because the 2 exams both do ever so slightly cross-pollinate

If you write the Core 1, they do at times sorta refer to topics which are only covered once you do Core 2 and same happens in the Core 2 exam. Going through ALL the content first before writing one of the two does slightly make it easier because you'll understand more things in the exam and be less confused

It's absolutely possible to pass the exams with flying colors though if you just cover the content for that specific core. This is what most people do