Around 20 litres/5 gallons is ideal.
Anything smaller (7-12 litres) really restricted growth too much in my experience.
Straight into the final pot to avoid transplant shock/hassles works best too.
Don't use a layer of stones on the bottom, this is where the roots end up and when they do, you want them to access nutrients, not rocks!
So, soil/coco all the way to the bottom and all the way to the top too, don't leave a great ditch in the top of the pot, the coco or soil will settle anyhow.