Churning bank accounts is an easy way to earn extra money if you have direct deposits. Banks will give you extra money when you open an account with them and deposit a certain amount of money within a certain time period. 

Investing is the best way to not only help fund your collection but also to secure your financial future. I would never recommend going into debt to buy Pokemon cards, but I have used earnings from investment gains to purchase a card. Covered Calls to generate small amounts of income.

Sell cards you pulled that you don't necessarily care about to buy ones that you really want. Better yet, hold onto to them until they appreciate in value and sell them then. Patience is key. 

By simply installing a plugin or visiting your respective cash bask site, you can earn money back from your every day purchases to put toward your collection.