Repot as in put in pot a little larger than this one would be fine. Repot as in knock all the dirt off, cut a third of the roots off would likely kill it if you are in the northern hemisphere.
The best thing to do would be put it in a larger pot in the sun outdoors, fertilize and water regularly, read up on how to design, and let the tree grow for at least two years. Five would probably be better. Wait until it has established some branches before trying to train them.