He’s not ready but its fine, this is the attitude you like to see from a young rookie. He’s been consistently improving and he is relentless on the court, often to his own detriment at this point, but as he learns how to harness it, it will be his greatest advantage.
Sacramento Kings would be a good team for you to support. They are a west coast team so it might be too late for the majority of regular season games but otherwise they are probably the best option.
As far as east teams, the Cavaliers and the Pacers are good options. Both teams play good basketball and have some extremely talented young players.
NBA fandom is different from football fandom, most teams are going to be playing more or less the same way with some variation based on personnel, which is why NBA fandom is predicated on stars. The game is 5 on 5 so one extremely good player has way more impact on a game than just about any other team sport. Its perfectly fine to watch games because you want to see a certain player rather than a team.
Yes its possible to buy tickets right before the game starts, you can even get tickets from scalpers outside of the area, although I’ve never been to San Francisco I think its a pretty safe assumption there will be scalpers there.
As long as you have tickets and the game is ongoing, you will have no trouble getting into the game.