Wondering how you got so many CP to reach Gold league? You paid by your own money or earned from the game with some certain investment?

Right now , I'm in Silver III. I bought all those cards in order to reach this minimum lvl to get Dec rewards.
However, I found the rewards on this league is pretty small so that I did not see a way to bring me to Gold league if I stop dumping money into the game.

So that's why I have this question.

By the way, my ID is @splinterbin
Thx for any answer.