People go to basketball games dressed up and others go totally casual. I just recently went to my first one (Clippers game VS, I don't remember) and my, my sister and her other friend wore nice jeans with a nice shirt and hills. But then again we had quartside seats. It depends on where you're sitting also.
But really like what jammin says, no body really cares. they are so interested in the game, it's just like watever. LOL.
But if you wana dress up, go for it!! : )
Have fun!!