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]
(..) I will not lose my only son. - You don't know the Dark Forest. - Then I'll find somebody who does. I won't abandon her a second time. The forest gains its strength from your weakness. Do you drink to drown your sorrows, or your conscience? What concern is it of yours why I drink? (..)2012 Snow White and the Huntsman