#1 FC Porto
Porto have arguably mastered the art of transfer dealings whilst reigning supreme on the pitch as well. In the last 15 years, they have earned €872.3 million in sales and have won the Primeira Liga 9 times. They also managed to win the Champions League and Europa League once.
The revenue they generate from the Champions League has been key to their success, and they have been a staple in the competition for more than a decade. 2004 was the breakout year in terms of sales for Port, as they sold Ricardo Carvalho and Deco for big money.
In the time since they have been followed by James Rodriguez, Radamel Falcao, Hulk, Pepe and many more. Unlike other clubs, Porto have sold a host of players for decent sums rather than just one or two superstars for huge deals. This has kept the sales ticking over consistently, enabling shrewd investment to guarantee success on the pitch.