They hope to make big 'gains' in Congress in the coming election. [=they hope that many more members of their party will be elected to Congress]
Her hard work 'gained' her their respect. [=she has gained their respect through hard work; they respect her now because of her hard work]
a stock that was one of the year's biggest 'gainers' [=one of the stocks that increased the most in value]
(..) Messala. A bet like that's not customary. And it's not appropriate. Not appropriate for who? All of those citizens who stand to gain when you beat my man? You will beat him, won't you? He's just a Jew. Oh, I'm sorry. I failed to mention that. But you've crushed an entire people. I should think (..)2016 Ben-Hur