you need to get your CENOMAR from NSO as well. your gf can request this for you through http://e-census.gov.ph it only cost 450.00php because it is now required for foreigners to have CENOMAR. Then your CNI from local registrar will be converter to consular office here in Philippines like in UK Embassy in Manila or at any British Consular office like the one we have here in Cebu.
Then when you arrive here in the Phils. you will need to attend a half day to one day seminar at DSWD, that needs to be scheduled or check the schedule at your local dswd in Davao.
Make sure that your gf got Brgy. CLearance, community tax certificate and 2x2 picture of you and hers. Photo copy of your passport.
Once you have every thing, including the certificate from DSWD, photocopy everything into 3 copies each and then fill up the marriage application for marriage license and pay the corresponding fees... you'll get your receipt and will be told to come back after 10 business days for your marriage license. after that you can get married either civil or church. But church like roman catholic, you have to present baptismal certificate if you are roman catholic, if not then you can convert to catholicism and memorize all the catholic prayers book for the priest and etc.
Good luck