I also teach grade 1, and I have found it quite difficult to reward them as they get distracted pretty easily. Stickers are all well and good, but with the case of my kids, they seem to have their own that are much fancier than the ones I can afford to give! They even give them to me!
Anyway, I'm trying this new reward system that I call "Teacher D's Dollars." I made fake money on the computer and printed and copied. They are in denominations of 1, 5, and 10. I have given each student an envelope, and when they are good I give them 1 dollar. They store them in the envelope throughout the class and when class is over, they return the envelope to me. At the beginning of the class, when I call attendance, I give out the envelopes. If they have 5 ones, they can exchange it for a 5 (which look fancier and are bigger than the ones), etc.
They seem to like it so far since they get to keep their envelope on their desk during class, count their money, etc.
At the end of them month I am thinking of doing a "marketplace" idea with the money; for example, buying small things like pencils, erasers, rulers, that they can "buy" with their money. I kind of have an advantage as I live in China and these supplies are extremely cheap.