You can find Giovanni Dos Santos in Barcelona's reserve list. Although he is only 69 overall, you can edit his stats and make him as good as Ronaldinho. You will then have two of the best midfielder's in the game.
When playing as a good dribblers such as Cristiano Ronaldo and Robinho, run downfield with the ball and, as you are running or juggling, rotate the Right Analog-stick clockwise once and your player should do the rainbow. Remember, do all this while running with the ball.
To get cheaper players at the end of the season in Manager mode, choose not to renew your contracts of the players you want to keep. When the transfer period starts, you can transfer them without paying fees and re-negotiate a cheaper contract.
To get infinite player creation points, go to "Traits" and select all the negative ones. Then, press A to exit the Traits screen. Distribute the given points to the category of your choice and then press A. Return to the Traits screen and de-select the negative traits. Press A to exit. Save your player and then reload your player in the edit player menu. Repeat these steps until your players stats are maxed out.