For sure I have no experience for this kind of matter but I do ask lots of question from them who has been through it.
I'm from Dusun ethnic and we have our own custom plus I'm a christian but I'm not a Roman Catholic.
Thus, based from my research and observation I found few info that could help my engagement preparations.
1) Gifts in engagement ceremony (hantaran)
In our custom, all set of gifts will be given by the bridegroom-to-be. Meanwhile the bride-to-be doesn't need to give gifts even though there are some of them do so.
List of gifts according to our custom and meaning of it :
(a) Umbrella - so that the man could protect his woman
(b) Fabrics (kain ela) & Sarong - so that the man be able to provide
(c) Full sets of woman's apparel - so that the man be able to provide
(d) Full sets of beauty products - woman's need to maintain their beauty
(e) Engagement ring - as to knot the tie
2) The purpose of engagement
It's a custom.
During the engagement ceremony, representative from the male will negotiate on how much the "berian" would be, costs and date of marriage with the female's family. After determine all, agreement will be signed (registration) and of course there's going to be exchange ring ceremony. During engagement period will provide time to the man to raise money for wedding ceremony until the fixed date.
How about the meaning of "tunang-kahwin"? (engage-marriage). Catholic actually didn't encourage this one. This was done when the male agreed to give "deposit" at least 10% from the amount of "berian" during engage-marriage ceremony. After that sign the agreement (registration) and a date for wedding ceremony will be fixed agreed by both families. When the engage-marriage ceremony done, the male can take his fiance to home (perhaps treat like a wife already?). This would give time to the male to save money for wedding ceremony (known as makan-belanja). When it is enough to conduct the ceremony then wedding will be held. This was done with reason when the man didn't have enough fund and the woman is pregnant (or not). Another reason is to speed up the marriage. However, during wedding ceremony only "blessings" will be given. The reason why Catholic didn't encourage this because engagement and wedding has its own sacrament.
It is true the concept of "tunang-kahwin" may reduce the costs and time, however, the most important in Catholic's marriage is the "sacrament of marriage". Couples also required to register their marriage under the law.
In engagement custom, both man and woman supposedly cannot live together like husband and wife (even though there are some break the tradition). If the woman found pregnant before marriage then the man will be fined (sogit). In this kind of case, of course both couple cannot held full wedding mass in church, however, may asks blessing only from church. Normally, they would conduct this blessing ceremony outside church such as the female's house. Catechist or Pastor will be called for blessing and as a witness. The one who is going to conduct the marriage could be "Wakil Ketua Anak Negeri" (WKAN) or "Ketua Anak Negeri" (KAN) or Ketua Kampung.
3) Full set marriage
Starts from "merisik" (inquire) until wedding ceremony. Higher costs.
4) Registration of marriage
From what I know, couples who is in engaged status went to register their marriage in law is not enough to declare them as husband and wife. They also cannot live together under same roof.
A wedding ceremony from church must be conducted (at least blessings) to announce them as husband and wife. There must be a declaration and agreed by both families.
In addition, after registration (normally at Jabatan Pendaftaran Negara) the law provide 21 days for them who against this registration of marriage. After 21 days' over, JPN will call out both couples and their witness to arrange simple wedding ceremony and soon after that certificate of marriage will be issued to announce them husband and wife. Some church are reluctant to conduct full mass wedding ceremony after they received certificate of marriage from JPN because church felt that law is turning them down. Therefore only blessing ceremony will be conducted.