Opening is a real grind.
However, once you can fill your first set it's trivial to obtain a cash injection every coin refresh. 'How?' you may ask?
Simple. sell your most common card and take out your most expensive card (keeping it on the desk). Buy another pack and open it to gain the most common card again.
The coin will reappear. Only now, you already have that rare card. So when the coin gives you the 'missing' card -- simply sell the newly spawned one for money.
You can do this trick for every subsequent deck type until money is trivial.