I'm very positive that what wins the game tournaments is Focused and Very Focused, not Confident. You need level 10 on the skill, obviously. If you research once or twice it seems to help "forever", so you don't have to do it before each tournament.
Now something I'm not sure of: I believe that the more time your Sim spends playing, the better they get. Might just be me, but it felt that way. He still loses some tournaments sometimes, or comes in second, but usually he wins.