Peja Stojakovic shot only 32% from deep his rookie season, at age 21. And he had played professionally in Greece for years.
Just keep gunnin', son.
Seriously though, the jumper will get better as the bullets fired count increases. Look at Quincy Douby. In practice, the guy could outshoot Reggie Miller. (Supposedly.) In live action ... nope. D.G. needs every opportunity possible to pull the trigger. He'll find his spots, his comfort zone, his flow. But only with opportunities.
Mix in some drives to the hoop, some fast breaks. He needs minutes, and shots, and opportunities. Plenty of all that. As such, D.G.'s goal should be to do whatever Coach Natt requires of him in order to get on the floor.