With LED Christmas lights becoming more and more popular, it is possible to get the old style mini lights for close to nothing. One thing to do is take a sting and wrap it in to a ball. When hung from a tree they look like fruit. I call then light berries. Take extension cords (the type that are maybe 6 ft long with a plug on one side and three sockets on the other) and have them branch (no pun intended) out all through your tree. Plug in the berries, power them up., and you have a light berry tree.
ps Pun was really intended.... sorry