Speaking as a Real Estate Agent….
It is not customary to give your real estate agent a gift at closing. It is however customary to receive one.
The amount spent on the thank you gift is usually decided on the amount of your agent’s commission, (and probably a little bit on how fun you were to work with). I like to give a customized gift basket that reflects my client’s special likes and dislikes. Gift cards, discount cards from local retailers, and flowers are all common gifts.
If you really appreciate what your agent did for you and would like to thank them for all of their hard work, you may consider writing them a thank you note that they could use as a testimonial in future marketing. You could invite them to your house warming party. Or best of all, you could tell every one that you talk to what a great job they did and remember them when it is time to buy or sell again.