If you own some knowledge of electronics and know how to solder, you can easily build a nice little Christmas string light circuit using some LEDs and a few other passive electronic components.
To learn how to make a LED Christmas tree string light, just follow these steps:
Procure some LEDs of different colors, ezxample red, green, blue, white etc. you should procure at least 50 of them.
You will find that these lamps have two legs, one a little smaller than the other.
The smaller one is called the cathode and the longer one is the anode, in simple words the anode isthe positive and the cathode is the negative points of the LED.
To make a string out of them, start joining the alternate legs of each LED with the other using small lengths of wire, cut into desired sizes.
Meaning, connect the small lead of the first LED with the longer lead of the next LED and continue this process until the last LEd.
Finally you will find that the two endLEDs have their one of their legs free or open with opposite polarities. One end LED will have a free positive and the other end LED will a negative leg free.
Next take four 1N4007 diodes and a 105/400V capacitor and make a small tranaformerless power supply out of it. You can find the circuit if you do a bit of Googling.
Finally connect the positive and the negative of your LED string to the above power supply terminals, yay...your LED string light is ready to be put on your Christmas tree.
CAUTION - DON'T FORGET TO INSULATE THE OPEN POINTS OF THE STRING LIGHT AS THE ENTIRE WIRING IS NOT ISOLATED FROM MAINS AC.