Trees don't grow the way people do. A three year old has arms a foot and a half off the ground. Ten years later they are four feet off the ground (in the US. In Europe and everywhere else they are a half meter and then 1 1/3 meter). A tree with a branch 8 inches off the ground (20 cm) will have that branch the same distance twenty years later (unless the branch dies). You can't look at the tree, imagine it three times as large, and wait for it to expand. You have to wait until it is as tall as you want and then shape it. Usually that means start with a ten year old tree, or maybe a lot older. You can get take a two year old tree and shape it up, but it won't be much thicker for a long, long time.
A good source of material is friends who are digging up landscaping plants or clearing land. You can do some work for the for free and get some pretty old stuff. I dug up a boxwood last spring (in my yard) which is about 50 years old. It is my big project this winter.