I started with two bamboo poles in each bucket for support since there is a field of it at work for free. Once the plants get tall enough, I add the PVC and roped the top of the bamboo to it.
The PVC is secured to the buckets with a zip-tie at the top of the bucket, and goes all the way down to the second bucket in which I drill a hole a tad bit bigger so it stays secure.
The soil I used this year I bought locally (Nashville TN) from Southern Nurseries and it was $50 for a truck bed full. Holy Cow mix
http://www.southernnurseries.com/soils
The plastic bags on top were flush until the mix got wet and it drooped down with the soil level. I use it more to keep mosture in and it seems to work well.
I fertilize each plant with 1TB tomato food per gallon of water per plant. I always fertlize pouring it from the top and not the self watering pipe. I then top off the self watering pipe every other day until water pours out the overflow holes.
Here are some pics from a few weeks ago. (sorry, dog always wants to photobomb my pics)