The city composts here, so you fill your bin with your leftover foods and the city collects it. In return you are allowed to load up on compost once per year.

I go to the local green house and grab large bins of soil (you shovel it yourself but in return it's cheaper). That usually works well. The only problem is it's not regulated for weeds! My garden is full of them and it takes a momentous effort to stay weed free.

I also use some tomato food for the tomatoes. Other than that just some water and love!