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]
(..) Correct. He said that this is our house, this is the police station and that's you. That's me? Yeah. He made you Chief of Police, so... I've gained pounds. - It must be the uniform. - It's the dangers of a desk job. I'd like to report a lost purse. Why don't you have a seat? (..)2009 The Lovely Bones
(..) MONTENEGRO: Not great. Frank encrypted his files, so I'm using counter-steganography to see if I can gain access to it. Let me know when you're done. Yeah. Uh, Angie. Yeah? I have something for you. (..)2016 TvShow: Bones Title: The Fight in the Fixer Season: 11 Episode 15
(..) best friend since i was i was not a popular child, you have to understand i had no friends before he came along hes the only reason i ever gained any fucking confidence but your no longer , your years old and unless your too blind to notice, hes not your only friend anymore (..)2012 Ted