The Kings of the Sea version of Joffrey Baratheon states that if he is the only king in play, he gets +1 strength for each gold on him. There is then a space and the following text. Response: After an opponent pays gold to marshall a character, put that gold on Joffrey. My question is this. If there is another King does he lose the response as well? If not then am I correct to assume that this gold will remain on him after the taxation phase as it is not in my gold pool? I am wondering if this card would still be useful even without the strength bonus as I would use the gold during plot, dominance and other phases to pay the gold cost of events

Even if I can't spend it and there is nothing that says that I can will it still count towards dominance?

Unless a card effect specifically says otherwise:

1. Only gold tokens that are in your gold pool are lost during Taxation.
2. Only gold tokens that are in your gold pool count toward Dominance.
3. Only gold tokens that are in your gold pool can be spent.

Joffrey's Response stays if there are other kings, but the gold on him doesn't do anything for you since it isn't in your gold pool.