Elin,
In place of the 1 gallons, I'd try using some 2 liter plastic soda bottles as the "starter" pots. Just cut off the tops, paint the bottoms with some plastic spray paint, poke a few holes in the bottom/sides, and it's an instant 1/2 gallon pot, and it's nice and deep for the roots. Also, if you don't paint the bottoms and turn it upside down, it makes a nice and tall humidity dome. They're about the cheapest, most durable, containers I've used and with every container purchased, you get a free 2 liters of soda! ;)
For soil, you should look into both vermicomposting (done with worms) and Bokashi composting (done with effective microorganisms in an air-tight container). Both can be done indoors, if desired, and with very little space. It's a great way to turn "garbage" into some nutrient-rich soil!