Hi. I want to understand how to calculate the gold bonus, and I have two players I don't understand. I have these 2 human characters, Natalie and Jason, with items that give gold bonuses. If I understand how they work that could help me calculate the rest and plan how to stomp the gray goo level. I have other gold bonus characters, too; but I want to keep this simple. Could someone help me calculate how to predict gold bonuses?

Natalie:
I have got a level3 legendary for Natalie called Scalie Silken Cloak of the Big Sister. It increases all gold by 200% plus 100% for each human crusader. (Its pretty great.) Natalie by herself with this scarf brings the gold bonus up to 500%, but I don't know how the number 500% is arrived at. She's human, so that's 100%. So far that's 300%, so I am missing where the other 200% comes from.

I have got for Jason a Tamahagane Steele sword that adds 50% of all gold...however if I put Jason in with Natalie then the bonus changes to 1250% -- and for each human added thereafter that bonus will go up by 450%. I think I am missing some numbers, because I don't know how to calculate the 500 for Natalie, the 1250 for both and the 450 for each added human crusader.

I also have other gold bonus characters, but maybe if I can understand these two then I can figure the rest out based on them.

All bonuses are multiplicative unless specifically stated otherwise. A 200% bonus and a 300% bonus are not a 500% bonus, they are a 1100% bonus. You can calculate as [(bonus A + 100) / 100 * (bonus B + 100) / 100 * (bonus C + 100) / 100 * ... ] * 100 - 100.