what our contribution influencing of winning chance?

Which indirectly influences your winning chances. Let's say, for a moment, there are a hundred people on Steam Gifts. Fifty of them have at least $1 CV and only ten have > $100 CV. If you are one of those ten, you have a 1:10 chance of winning a $100 CV giveaway, whereas you only have a 1:100 chance of winning a non-CV limited giveaway (and 1:50 for a $1 CV). This is, of course, extremely simplified, doesn't take into account demand for particular games or how many people already own it, but it should get the point across.

But yes, having more CV won't make you any more likely to win a giveaway, you don't magically get to press a win button because you have a higher CV or anything, you just so happen to get access to more exclusive giveaways and thus have better chances to win. Not that I'd really recommend going on a CV-boosting spree right now if your only goal is to win giveaways though, considering the whole system will be done away with soon.