The hard part about this is getting the lives to begin with. This is what I wrote in the "get 9 lives" and "get 15 lives" achievement guide.
Honestly if you play on easy you wont have too much of a hard time doing this. If you decide you want to start by playing on hard, you will. Simply replay the first level, accruing gold (or whatever it is) and finish the level. Rinse and repeat. Repetitive? Yes. To the point? Yes.
Honestly, although this might seem like a waste of time, keep in mind you are also leveling up your character, so it isn't horribly inefficient.
Then just play one of the levels and jump off a cliff or something. Not hard, but you might want to wait till you beat the game to abuse it. But that's up to you.