A few unit’s I have been at have had a “Cup and flower fund”
where if you pay in you get a gift when you leave, if you don’t you didn’t. both ways work....
There's usually a fund set aside for farewell gifts, but the ones that are warranted for them are a matter of protocol, which is very biased, but that's up there with the awards process as well...Moving on...
Personally, when my Soldiers would depart, it didn't mattered what their rank was, they would get something that symbolized their commitment to my team and our organization as a whole, no matter how big or small. As far as the funding goes, it is an entirely optional process and no one should feel compelled to contribute. It should be a donation based type of funding.