Another option for gifting Home Depot funds to someone is to send an eGift card electronically.
This kind of gifting system cuts down on having to return unwanted or inappropriate gifts.
Since gifting for an engagement is not required, the general rule is to spend whatever you can and whatever is in your heart.
For symbolic jewelry, a groom may choose an aquamarine engagement ring for his bride's birthstone or a husband might mark his 19th wedding anniversary by gifting his wife with an aquamarine eternity ring.
For example, on SmugBox there is a "Giver" cheat that is described, which involves creating a second Farmville account (called the "giver") and then basically gifting your main account with as many items as you can.