I think Cpt Weird was answering CX-330's question about the stage 1.
However, to answer your question, here is my 2 cents:
1. Just read up on all matters YOU think is important to be an commercial jet pilot(Technical, Airmanship, etc).
2. Know yourself and where you are coming from. More importantly, try to understand what you are getting into with this program and living in HKG.
3. Read all about CX (just make sure the sources are traceable and authentic)
4. Be humble and modest to your interviewers, but stand your ground if you know what you are talking about. 
I am quite bad at diagrammatic tests and mental math question, any books or things to recommend?
Try to get hold of an basic high-school math book. It should help you with some fundamentals. It also teaches basic shortcuts for adding, subtracting, multiplying and subtracting. You can try this website for some basic practice: Numeracy Test
As for the logic reasoning test. Try this website:
http://www.iqtest.dk/main.swf
It is somewhat similar to the test they use at Stage 1.
Remember these are just my 2 cents. Whatever works for you is the best option.
Good luck!