I highly agree with Sactownkid about usage. You just need to keep feeding him the ball. He's a scorer, but he's inexperienced. He'll have nights where he might go 5-18, but you can't discourage him by limiting him to 8 shots the next game. Let him loose and let's see what he can do.
However, he'll need big improvements if he wants to be a #2 scorer in the NBA. Defenses would begin to gameplan for him which would bring a whole different dynamic. He's athletically limited. He has a very slow first-step that catches no one off-guard. He struggles to get to the rim, which means he'll have to make it up elsewhere. First, I think he'll need to tighten up those handles and improve in his overall ball handling. Not only will it help him get to the rim more, it'll also help him with creating space. It'll expand his offense to a whole other level. A big part Buddy is missing out on right now is his rim attacking. He doen't get to the rim enough. If he can get that 3-level scoring going, he would be golden. He needs to get his FT rate up, it's seriously lacking for a guy who has as much usage as him. Secondly, I think he needs to improve on his off-ball movement. We don't see him shoot enough off screens. We often see him put the ball on the floor unnecessarily, especially in the mid-range. Playmaking and creating for teammates isn't a big deal for me. Klay averaged only 2.5apg this year. Last season Beal only averaged 3.5apg(this year he's at 4.5apg, but that's only because he was forced into more of a playmaker with John Wall out).
On defense, he'll just need to keep putting the same type of effort we've seen in the last 20 games. It's all effort and IQ on that end for him.
For him to make a big leap, he needs to be able to create his shot consistently, while being decent on defense. However, he can't do this if he isn't given the opportunity to. I've always pointed to Devin Booker when it comes to Buddy Hield. Booker is a player who's athletically limited in the same way Buddy is, but he's already a lot better despite being 3 years younger.