it is better to start small, because the roots will grow down, and jumble at the bottom, if you continueously transplant plants (correctly, smaller to larger) the root system will be much larger and spread out. Imagine this,, the roots shoot to the bottom like food coloring in water, and spread when they hit the bottom and then spread throughout, if you start small the roots will spread through one container than if you put them in a larger container they will shoot down again and spread throughout the larger container. In a simple grow I use a cup for sprouts, a medium pot after, then a larger pot, then a bucket....or outside!!!