Best way to get the enough points to get gold is to use your skill points to purchase the a random starter accessory. Then keep reloading the game until the random accessory you get is an angel doll. This way you start with an angel doll. Use it right away on the turret that you plan on upgrading first.
The only level I can't get on the bonus mode is 34. Just a hint to people trying to get them all: You can balance balls on top of each other (up to about 8 or 9).
Oh, I guess someone also picked up on the LF2 thing ;) And Blackhawk808, it's the SOUNDS that are from LF2. The music is not; but the sounds from things blowing up, collecting capsules, dice bouncing, etc. are from LF2.