if you are studying full time then I guess at least 4 months required because you need to cover all the aspects from the syllabus and do a lot of practice from past questions
for example
the syllabus is part into 4 sections sec A - costing sec B - decision making sec C - budgeting and standard costing sec D - performance measurement
so it should take at least 90 to 100 days to cover and practicing a lot of MCQ MTQ would really help you to pass.
