First, just keep beating on everyone with a ladder. Click the right analog stick then spin it to clear the ring out. Place the ladder in the centre of the ring and climb it. Just hold onto the case for a while then jump down before you are tossed over. Now just keep on repeating again and again. All you need to do is keep trying, without letting the AI controlled players climb the ladder. Clear the ring, climb the ladder, grab the briefcase, jump down. Rinse and repeat.
Note: You will not be assigned straight into the Money In The Bank match unless you've won the majority of all your matches. Simply edit all the superstar's rosters until there's only enough for the Money In The Bank match, then you will be guaranteed a spot in the match.