You guys are so smart! Several of you mentioned wine crates, which kind of steals my thunder, but I'm glad to see that we're on the same page. I would have loved to use the self watering containers that Christina recommended (see them in use here), but my odd space constraints made it difficult (my patio is very long but not terribly wide).
We already had a storage rack sitting outside on our patio, and I wanted to use it if I could. Luckily, wine crates fit on it perfectly.
Craigslist came through for me, and I scored 11 wooden wine crates for $39, which gave me 6 extra to use as storage on the lower levels. They are pine, so they will deteriorate eventually, but pretty much anything you fill with dirt and water and leave outside is going to do that. I considered treating the insides or lining them with plastic but ultimately decided it would only slightly prolong the inevitable.
Prep: My uncle saw my wine crates and immediately worried that they needed to be reinforced to hold up the extra weight. He screwed little rectangles of wood in each of the corners for me! We drilled holes in the bottom to allow for drainage and then laid down a bit of old screen to prevent soil from leaking out.
Planting: Fill with good potting mix, add your plants and plenty of water to get them started. I also tried some seeds. I have no idea if they will take, because all I did was sprinkle them and then put a bit of soil on top. We'll see. I'm not exactly an expert gardener.
See those funny little terracotta things sticking out of my planters? They are called ollas (oy-yahs), and they are a very traditional way to water in the southwest. For more detail, check out this wonderful post about using ollas. Basically, they drastically reduce the amount of watering you have to do, which saves water and effort.
Olla sources: Mine were given to my by my mom, and she purchased them from the local nursery Tree of Life. I found Arizona Pottery to be the most reasonably priced online source.
Technically, this didn't break my shopping hiatus, because the wine crates were repurposed and my mom treated me to the soil and plants because she was so excited to see I was finally going to start my own garden. If I had done the purchasing myself, it would have been about $35 for the gardening supplies, plus the cost of the wine crates and the ollas.
What did I plant?
Sage + greek oregano - both perennials, which means I shouldn't have to replant next year
Rosemary + mint - also perennials, placed together because they are equally invasive and I figured they could hold their own against each other
Basil (two different kinds) - annual, will need to be replanted each year
Cilantro + red bell pepper + Italian parsley - annuals, will need to be replanted each year
I'll make sure to post updates so you can see if I manage not to kill everything.