Score modifiers are your friend: Aim to get the red bricks which unlock each one, and have all of the ones you've unlocked on at once. The purple stud which appears next to the shop normally gives you 150,00 or so, so with modifiers:

2 x 15,000=30,000 2 x 4 x 15,000=120,000 2 x 4 x 6 x 15,000=720,000 2 x 4 x 6 x 8 x 15,000=5,760,000 2 x 4 x 6 x 8 x 10 x 15,000=57,600,000

That's a lot of studs! Unlocking all the characters/hints only costs around 4,000,000 total, so you're all set.