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]
(..) Wait a minute. Everybody else has forgotten the truth, - why do we still remember it? - Truth or consequences. Wiccan rule, right? Prue cast a spell for her own personal gain, now we have to deal with the fallout. I'll be right back. I need to remind Martin of something. You go, girl! (..)1998 TvShow: Charmed Title: The Truth Is Out There... and It Hurts Season: 1 Episode 8
(..) No, no. I mean I can't believe you actually took my advice. The biggest pooper at the Wicca party has finally used her power for personal gain. It's about time. Personal? It's affecting us. Prue, what have you done? The spell was only supposed to work on me, okay? It said, "those in this house." (..)1998 TvShow: Charmed Title: The Truth Is Out There... and It Hurts Season: 1 Episode 8