The cheapest way to get a ICAO country PPL is to study at canada ( comparing to USA, UK and australia. I was studied there too. For the whole PPL, it is just round HK$40000-$45000. you can go to www.proifr.com to have a look or ask me for more information.
What do you mean ?
Do you mean u wanna study PPL theory on ur own ?
It's fine to join those ground course held by HKUSPACE, HKAC, HKACC...
I dont know is there any way to apply the theory exams by urself, so joining training course will be the easiest way for you.
But if u mean u wanna have whole PPL training, even if u can pass the PPL theory exam. You still need to have your flight training. For flight training, there arent much choices in HK (HKAC is too expensive !! $50,000 for membership fee only, plus training fee)
So if you wanna have you PPL in a faster and cheaper way, u can choose to study that overseas. Both Australia and Canada are good choices....
About the textbooks for PPL theory subjects, maybe u can go to have a look in an aviation shop located in North Point. I'm sure u can find you u need.
參考: My experience (I am having my PPL training in SYD right now)