This won't take as long as you might think.
You should have this after completing both games. I had 6500sp after completing Shadow Over Mystara, then I played Tower of Doom. Just like with challenges, progress from both games is counted towards the 10,000 goal.
You will earn VP by completing challenges while playing. VP is used to unlock things in the Vault. Start playing either game. Once you've earned about 200VP, quit and go to the main menu > Vault and scroll all the way down past the concept art. There are some modifiers you can unlock and then turn on when you play the game. Make It Rain costs 200VP and makes enemies drop considerably more silver.
Start Arcade Mode for either game, press Y before starting the game to modify house rules, turn on the option for more silver, and you'll make much faster progress toward 10,000.
(I don't remember if the game started with any VP, or if you are at 0 until you earn some by doing challenges by playing. So you could also check the Vault to see if you can unlock Make It Rain before you start the game the first time)