Container gardening is a great way to grow tomatoes, peppers, cucumbers and many other plants. The trick is watering them. If they dry out once, the plant is pretty much spent. After many experiments this is what I came up with as a way to grow tomatoes on my deck. Total cost, with plants and soil, is about $20. It's not 100% self watering but it is an extended watering container.
Purchase 2 - 5 gallon buckets at Home Depot or Lowes. They are about $5 each. You will need a small bag of pebbles, some moisture control soil and a plant. Drill holes as shown below. I suggest using that pattern. Your tomato plant's roots will grow through them and reach the reservoir.
The bucket with holes in the bottom is to the left. That is where the plant and soil will go. In the 2nd bucket, fill the bottom to about 4 inches with the pebbles. 4 inches is about the gap left when you place one bucket inside another. You want the soil bucket to rest on the pebbles. If you look closely you will see holes just above the pebbles in the 2nd bucket. Those holes are your overflow holes. You don't want the bottom of your soil bucket to be soggy and sit in water. Drill about 4 or 5 holes around the pebble bucket. The holes should be just above the pebble line.
Place the soil into the soil bucket. It is the bucket without pebbles and has the holes in the bottom.
Plant the tomato in the soil. I am filling the pebble bucket with water and Miracle Grow. Fill it to the top of the pebbles, just below the run-off holes.
Drop the soil and plant bucket into the pebble bucket and water it.
On a hot day a single 5 gallon bucket will dry out in a day or a day and half depending on how large the plant has grown or is growing.
Using this method you really can get 3 - 4 days between watering (depends on plant size). Each time you water, soak the bucket. You want to make sure you see water come out of the run-off holes. The key is to keep the pebble reservoir filled.
This year I have one bucket of this design. In the bucket are 3 yes 3 Florida Basket Tomatoes. They are compact determinate tomatoes. The are producing a ton of fruit. I'll get a picture up next week some time.