I am currently the "head" room mom for dd5 Kind. class.
For all my kiddos so far, I have done room mom for K and 5th. Not sure why I picked those years, but I love being K room mom.
The K school setup here is very nice. One "head" room mom, and two assistants. Parties for Halloween, Christmas, Valentines and end of school.
School provides 10 dollars per party budget and we are on our own with no restrictions or guidelines for the rest. We live in an area that is VERY economically depressed, so we do get some kids that REALLY enjoy the parties as they dont get much of anything at home.
Christmas party consisted of me getting plain undecorated cookies from the bakery (cant be homemade), tons of icing, sprinkles, etc., with which the kids had a great time decorating and consuming and generally making a mess

. Juice boxes, bingo and of course there were several parents that sent in treat bags of candy, etc. which the kids happily took home. I pay for the parties myself, and the other two room moms usually provide something (one is really crafty and stamps up some beautiful little takehome bags with the kids names, etc.) All parents are always welcome.
While I would love to go overboard, I show some self-restraint, as it is my own personal opinion that sometimes going overboard sometimes discourages others from getting involved or offering their input if what they can offer may not be as expensive or time consuming. I also think making sure the napkins and plates match is NOT important.
We also do two school wide activites per year, which takes collaboration and planning. We did Polar express day with the kids wearing pjs to school, the cafeteria being set up with train style seating, Santa coming to the classrooms and handing out "tickets", the kids watching the movie all together and the cafeteria ladies coming down the aisle with the trays of hot chocolate. When it was over, Santa gave out the first gift of Christmas, and two names were drawn (a boy and a girl) and they were given copies of the dvd to take home. Each kid got a photo with Santa (we used one hour developing) and was presented a bell to wear (strung on yarn). Total cost for the entire school was under 100 dollars, including photos, hot chocolate, dvds, candy canes and coloring books (so about 75 cents per kid). It was paid for out of pto budget, and the dvds were donated. The kids had a wonderful time.
No group teacher gifts are allowed.
Dd gave her teacher a gift outside of the classroom as not many kids give gifts and our teacher is so incredible and has gone way beyond expectations that we did spend a little much and didnt want it to appear like we were trying to outgift everyone else.