How to use the gold card.

The gold card is introduced at level 41.
This is a very useful tool for increasing your score.

The gold card doubles your score for every card for 
10 moves after you pick it up.

So logically you should pick it up EITHER at the start of, or during, a long run, or before you pick up the scarab cards.

Uncover the gold card/cards if you can but try to save picking them up until you have a run. 

Leave odd cards on the table to make a run later.

The scarab cards are worth 1,000 - 2,500 points.
So if you can include them in the ten cards after you pick up the gold card that could hugely increase your final score, especially if you have TWO gold cards.

That's QUADRUPLE points. 
Up to 10,000 for the 4th scarab card.