I plant Tomatoes in whisky barrels but any container 15gal or larger is ideal for tomato plants. Whiskey barrels are about 25gal. I use a mix of 50% mushroom compost and 50% good sterile potting mix no dirt then add one good cup of bonemeal and a half cup of bloodmeal.
Remember to grow good tomatoes in a container nother smaller than a 15gal size container. Anything else would be a disappointment.
This is an early plant about 8 weeks old with a good root system. This is what I try to provide to area nurseries so that eveyone can get a good head start on the season before the plant and flower shows were I have smaller younger plants. I plant my cherry tomatoes in the barrels first part of April but any type of tomato plant will do fine planted in a container. Plant the plant deep about halfway in the ground this will allow a good root system to develope all along the stem. Remember the more root there is the more tomatoes there will be.
Cage and support
Finally add a good support. I use concrete reinforcement wire for my cages. This fits perfect in a 30 gallon or bigger container. This wire cage also gives plenty of room and support for the cherry types which I don't prune and the holes are big enough to reach in and pick tomatoes. It is also possible to use a single stake about 6ft and this would apply to all larger fruited tomatoes but not cherries. When growing anything other than a cherry type only allow 2 main stems to grow and remove all other limbs as the plant grows. This also applies when planting in the ground vice in a conatiner and using a single stake system. When ever a single stake system is used only allow 2 limbs to grow and tie once per week and remove all side shoots leaving only the two main stems to produce fruit. This is really important in a conatiner, fruit production will be low do to all the energy going into making a large plant that just doesn't have the root structure like a plant in the ground would have so only let two stems grow remove all other limbs.. I have 12 barrels lining my driveway each containing a different cherry/salad type tomato. I also add drip irrigation on each barrel for watering. Come late June when the plants are to the top and bearing fruit they will need water each day sometimes twice so drip irrigation is nice to have.