You may want to contact Oracle Philippines through this website: https://www.oracle.com/ph/corporate/contact/index.html or call 479 1000.
1. Can I take exam directly instead of taking a training first?
Yes. Attending training is recommended before taking exam.
2. Correct me if I'm wrong but it is a lot cheaper if taking exam only than taking training first.
Yes. You may want to learn first about the technology you want to be certified on before taking an exam. If in case that you fail an exam, you have to purchase another exam voucher in order to retake it again.
3. On Associate Certification, is it really mandatory to pass "Introduction to SQL" type of exam before training to "Basic DBA tasks" type of training?
No. There are no pre-requisites in training however, there is some sort of knowledge already expected depending on the training offered.
Hope it helps a lot. By the way, I am Pinoy as well and already took training and certification from Oracle. Glad that you are interested being certified by Oracle.