Like with any opportunity to give gifts, sending a gift to someone who is just receiving her GED is not mandatory. If she will be holding a graduation party that you will be attending, it is customary to bring some sort of gift for her. However if you receive an invite but RSVP that you will not be attending, you are not obligated to send a gift. For close family and friends, you may want to send along a gift anyway, which is perfectly acceptable and likely very welcome by the graduate.
The guidelines for giving a graduation gift and giving a gift to someone who has just completed his GED are very similar. The important difference is that a student who chooses to complete his GED was likely faced with challenges that prevented him from completing a conventional high school diploma. This can make the experience that much more significant to the graduate, so a little extra thought in the form of a handwritten note in a card can go a long way. Showing that you recognize the graduate's accomplishment in completing his GED will mean a lot to him, and the thoughtfulness of the gift will be the most important part.
In many cases, a GED graduate isn't a teen, she's an adult who has some life experience, and you should choose her gift accordingly. If the graduate is the same age as a typical high school student, the same sort of gifts you would get any high school graduate are acceptable. However if she is an adult, try to find gifts that reflect her stage of life. If she has children, a graduation portrait of her and her children might be the perfect thing to give. If she is already working, a new briefcase for her job could be ideal. Whatever the situation, take the graduate's age and lifestyle into careful consideration.
Regardless of the graduate's age, there are some gifts that can always be considered appropriate. Many people choose to give the graduate cash in order to help him out in the next stage of his life. This is perfectly fine, as long as you accompany the gift of money with a thoughtful card. Gift certificates serve the same purpose, with the added bonus of being able to tailor the gift to the specific needs of the graduate. Choose a store where the graduate might need to shop for the next stage of his life, such as a clothing store for business clothes, or a home decor store to decorate a dorm room. Books are also a good choice for a gift, particularly financial and life-planning ones.
As with any gift, spend as much as you are comfortable with. If you want to try and get a larger gift, see if there is someone else you can split the cost with. This way, the graduate can get something she really needs without the gift-givers having to spend a small fortune. You may want to spend a little more on the graduate if she is a close friend or family member, but don't feel the need to spend beyond your means, regardless of who is graduating. The gift is simply meant to be a token of recognition for the graduate's hard work.
It is just as important--if not more so--for graduates to follow etiquette guidelines when they receive gifts from family and friends. If you are the graduate receiving gifts, the best way to acknowledge how much you appreciate them is to send out a thank you card. These should be sent within 2 weeks of receiving a gift, whether you received the gift through the mail or at a graduation party. Sending handwritten thank you cards is the best way to show your appreciation, but if you are sending out a lot of these cards, printing out your own or getting them printed professionally are also options. If you do use cards with a printed verse, be sure to include a short handwritten note mentioning the specific gift, and sign your name. That way, the gift-giver knows that the time he took to select the gift was well spent.