If you cannot get to a piece of gold, think about getting an enemy to go there and get it. Even think about using an enemy's head as a bridge to get across a pit or precipice.
In some levels there is a nugget that must be collected last of all, because you will need the hidden ladders to get away from that position.
In some situations an enemy can be killed without giving up the gold he is carrying. The gold becomes a “lost nugget”. You score no points for making an enemy lose a nugget, but at least you can finish the level.
If there is nowhere to dig, keep the enemies running over concrete and the tops of ladders and so make them release their gold at random.