Jean Scott also addressed this topic in "More Frugal Gambling" and she made a few wise suggestions:
1. Ask what the policy is about gift-giving to hosts. Some casinos will let hosts accept cash gifts, others non-cash gifts, others gifts that can be shared by all, and still others will not allow employees to accept gifts at all. Check to make sure you don't inadvertantly get your host into trouble with management.
2. When Jean asked a number of hosts what they most valued as gifts, they mentioned cash, gift cards, sports or race bet tickets, and food comps. Not particularly valued were candy, alcohol, clothes/accessories, and knickknacks.
3. The most valuable gift you could give a host would be your appreciation, especially if it will help him/her along the corporate ladder. A simple thank-you note, a letter of commendation sent to the host's supervisors, and especially recommending new clients to the host were mentioned.
Hope this helps!