Most Helpful Guy
More than likely your best bet is to move on. In most cases being too busy is more of an excuse than a reality. He might be busy, but if he was really into you he d make time. Since it's been a month id vote it's more of an excuse so move on..
Most Helpful Girl
I think maybe give him some space, I know it's hard because as a girl our feelings are strong and we want to take action the first confident chance we get, but don't. Be friend's, keep in touch moderately, let him make the moves... once he makes the move it's okay to make a move back and start slowly.
Just start as friend's. If anything is to happen, it first starts as friend's.
Maybe instead of a call send a text "hey, how are you? "How's your day?" Then... wait a good moderate of a few minutes and reply back. You don't want to seem rushy he might not like that.