LEGO Harry Potter Collection

For this achievement you will need to have at least a multiplier of x1092 (The x4, 6, 8 and 10 Extras from Red Bricks) will be even easier with the full multiplier of x3840. You will need to find the Red Bricks in Hogwarts. However if you want to get this quick you can use the other cheats (Note you will still have to go find the Red bricks for the ones you unlocked using cheats for the 100% Red brick achievement)
Here are some cheat codes (Will NOT affect achievements)
Red Brick Locator 7AD7HE
Score x2 74YKR7
Score x4 J3WHNK
Score x6 XK9ANE
Score x8 HUFV2H
Score x10 H8X69Y
Those should help you speed up the process. (Cheats are applied from Diagon Alley upstairs in Wiseacre's Wizarding Supplies)

Once you have your multipliers added start any mission from The Leaky Cauldron and choose Free Play and get destroying to collect those studs.
Will unlock upon reaching 10,000,000 studs collected.