While maids,bartenders and servers make the most. Gardeners and other staff barely get anything. They will appreciate it much more as they don't expect it. Maids and servers do expect it from everyone though. In fact, if you don't tip a server or bartender then they will just avoid serving you.
Some also will only serve those who pay the most. I've stayed at a 5star resort where 5CUC at minimum a day would get a server's attention. Anything less and you can eat your meal with no water/drink refills. Some of them make as much in tips as servers in North America.