Don't know what to do about school and life... Please help?

I'm 15 years old and in my second year of high school right now. I don't have any friends at school only outside of school. The people I sit with at school and talk with are only acquaintances. I don't talk to or hang out with any of the people I sit with at lunch. I don't like doing homework and I usually procrastinate it until late at night then finish it and go to bed. I don't like school either because my cles are starting to get hard and I will have to study a lot to do well in school. I wanted to be a stock broker or bond trader or anything in business when I am older but I just watched a program on Heath Ledger and it interested me into going into acting and I have been reading about other celebrities like Ashton Kutcher who was at a bar one night and a modeling agent came up to him and convinced him to go into the model show that was coming up and he did and he won. That is what started his acting career and that happens to a lot of celebrities that are famous today. It is about being in the right place at the right time. I don't know if I am good enough to be a famous actor but I think it would be an exciting job. I get sad a lot because I don't have friends at school and I can't figure out what I want to do when I am older and school is hard and I sometimes don't feel like trying and I just want to give up. Please help me. Thanks!