Hello dear, 

The syllabus of jcece and jee mains is approximately same. If you have gone through the topics of jee mains then your work is done, I have provided the link below to check the syllabus for jcece. There is no fixed preference for class 11 and class 12 topics the trend changes every year ,it will be better to go through the topics of both the classes parallely.You should go through the previous year papers of jcece in order to get good idea about questions as most of questions are copied from previous year papers. 

https://engineering.careers360.com/articles/jcece-syllabus-sample-papers.

Hope this helps you.