Hello.

1) Statistics
Sher Muhammad’s book (Vol1 and Vol 2 both) for statistics is enough. Solve past exams of at least 5 years making notes for theoretical portion.

2) Applied Maths
No single book covers the whole syllabus as you might have noticed that the syllabus is quite vast.
For mechanics portion Q. K. Ghouri’s book is enough.
For other topics you can consult any book you like.
I recommend using Zill’s book for ODEs.
As for any other mathematical exam, practice is key. I also suggest to be comfortable with integration and differentiation techniques before starting applied maths prep.

The full name of the books I have mentioned can be found in the suggested books sections of CSS syllabus for these subjects.

Good luck.