I just completed my first mini tree. I used 1/2" "flex" pvc from homedepot for the base. It comes in 5' sections, I used one complete section for the base of each tree.
1- cut the flex PVC into three 20" pieces
2- Pre flex the pvc by hand into a curve to make assembly easier
3- place a 1/2" "T" in between each section to join them
4- I drilled a hole thru each side of the T and corresponding flex piece and secured it with a zip tie
5-cut 3 pieces of 1/2" gold line pvc at 3 feet each and insert in the upright hole in the T fittings
6- insert 3 foot section of 7/16 dowel rod into each piece of PVC for added strength
7- Then drill a hole thru the top of each tree section and secure the three together with a zip tie ( I filled the exposed end with latex caulking to seal them up)
8- spray with krylon fusion green paint
As for wrapping the lights, this way worked out nearly perfect for me. I used Philips 100 bulb mini light strings from Target. One string each of red and green. Measure from the base of the tree and make a mark every 3 inches up one of the "legs" of the tree. Wrap your first color lights around zip tieing at each mark. Then follow up with the second strings in between each of those.
(Please ignore the zipties ends, I just finished it and was excited to show it off so I hadn't had time to trim the ends off yet.)