If you attend the wedding banquet of your elementary school classmates, it is recommended to give a red envelope, because people are relatively realistic these days. If you are invited to attend the wedding, you may be considered for financial reasons. If you have a good relationship with your classmates, in order to express your blessings, it will be more special to give a gift at the same time as the red envelope.
For wedding gifts, you can give some practical things, such as bedding sets, a pair of plush teddy bears, exquisite porcelain tableware, small appliances, home decorations, wedding crafts, personalized puzzles, real wedding dolls made from real photos, etc.
I especially recommend music boxes made of crystal and piano-shaped. The key is that the wedding photos of the bride and groom can be customized by laser on the crystal, which is very creative and romantic and worth recommending.