Since you are all good friends, you must give a small gift to them for their engagement.
The key to gift giving is to make the recipient like it, so that the gift is meaningful. Since you know both the bride and groom, choose a gift that both of you will like. For example, it is good to give some couple dolls, decorations, couple cups, tableware, etc. These are all suitable as engagement and wedding gifts. Here are a few recommendations: couple dolls customized with real photos, wedding Tang suit teddy bears. You can also give a very unique music box. You can also give traditional wedding gifts such as bedding.
If you go to their engagement banquet, it is good to bring a bunch of lilies, which means a happy marriage. Although the gift is light, it can represent deep blessings.
I think it is better not to give home appliances for engagement. You can wait until the wedding, then you should not only give gifts but also a big red envelope.