Gold earned is calculated from your score after a run.
Character Gold Bonus is already included in the aforementioned score. (No double counting. i.e. No score influence calculation and then gold influence calculation afterwards. Both are applied with the score.)
Riding Pet Gold Bonus is already included in the aforementioned score. (No double counting)
Summon Pet Gold Bonus is added to the final gold amount.
According to blog comments elsewhere, there is a cap on the max gold you can earn per run on a White Tiger. According to the comment, the "cap for the tiger is 7650 gold per run. Which means only 3825 gold for other non evolved mounts and 5100 gold for evolved mounts."