When The Boy was about The Baby's age, we were right in the thick of graduate school, before teaching assistantships and fellowships, and we were strapped for cash.
We wanted the kids to know something about the giving part of Christmas, too, however, so we took them to a dollar store and let them each spend a dollar or two picking out a gift for each sibling and Dad and Mom.
One of the best gifts one of the girls picked out for her little brother was a package of poker chips and some disposable tupperware. We cut a slit in the lid of the tupperware. The Boy spent hours putting the poker chips through the slit.
His sister now loves playing with it just as much as he did.