My opinion is it depends on the show and my mood towards the others involved. In college I did several dance shows and I found the dancers to be great to work and i wanted to get something for some of them i considered friends. Well ultimately i didnt think it would feel right if i got something for like 20% of the cast so since i couldnt afford flowers I made up a little card on my computer that was simply a red rose and inside said:
"I couldn’t afford a real rose for everyone on opening night, but this one will last a lot longer.
It’s been a pleasure working with you.
Merde,
Your Stage Manager"
Then on opening night as a way to relax I sat down turned on some music and just wrote each persons name on each card and signed each one personally. I had space to add in extra notes to certain people but it was a simple way to let them all know i enjoyed working with them. And at the cast party so many were all like "awww that was so sweet of you, thank you." which made me feel special.
When I ASMed one of my first shows during tech the SM got a little stressed so at some point during rehearsal he was always like I'll go buy a bottle of vodka and have a bloody mary and then relax. The next day I would ask him how the drink was and he always said he never got out to get the vodka. So opening night came still nothing so i collected a couple buck from everyone on the crew and at the cast party I gave him a really nice bottle of vodka and simply said "since you could never get it yourself we got out one."
One dance show I gave each of the 4 choreographers a bottle of wine, and the next show with them I had 4-5 bottles of some alcohol given back to me. I SMed a community theatre show and my thanks to the cast was just something I wrote up myself that just reflected on how the whole process progressed written in a form that kinda parralled our process to events in the show, printed them out and hung a few in the green room for all to read. As an SM for my last show I came in the first day of tech when they just moved in the space and helped them get a lot done and I got a card that I found hysterical of a guy standing under a falling donkey and inside it was just "Thanks for saving our asses," (plus after the shows people often bought me beers at teh bar.
So really there is no set rule of what to do its really all a personal preference. I like doing it caue I like to let others know they are appreciated for what they do (very important to do for the crews cause they are often under appreciated and they do the work anyway.) I also know I appreciate when someone hands me a small gift to say thank you, so I like to be able to let others feel that appreciation, and every show warrants something different.