How do i unlock new clothes?

You need to get an invite to play in a sponsership match on a cruise ship. If you have, then play the match on the ship against whichever pro tennis player that is there. If you beat him/her, you unlock lots of new clothes and stuff.

I'm on amateur mode, and I had to beat Maria Sharapova. And don't worry, they are really easy to beat in the cruise ship! My brother had to play Amelie somethingsomething, and he said she was easy.

Hope this helped!