A nativity set, or creche, is a gift that reminds people to focus on the birth of Christ, during the holiday, and that is also decorative.
One year my family made some simple stables of scraps of wood, cutting and nailing and glueing, till a stable on a wood platform was created. We left the wood plain with just a spritz of gold spray paint, purchased inexpensive nativity figures, and gave these as gifts to relatives and friends.
The three essential figures are Mary, Joseph and the Christ child, and other figures as you desire, like sheep, shepherds, camels, wise men and angels. Children like to add the figures to the scene day by day; first the animals in the stable, next the Holy Family and the baby Jesus. Later they can add the shepherds and their flocks, and then the Wise Men and their camels as they follow the star to Bethlehem.