I can contribute 10 bucks here and there, but I want to know every avenue I can make a difference
We used to have a GD Presidential. We should separate elections news (2017 too) with the rest.
There's a general article on "United States elections, 2018". It has links to the daughter articles:
* "United States Senate elections, 2018"
* "United States House of Representatives elections, 2018"
* "United States gubernatorial elections, 2018"
For example, in the section about Wisconsin in the House article, you can see who's announced against Paul Ryan so far.
Some of the more high-profile races have articles of their own. For example, in "Florida gubernatorial election, 2018", you can see that Rick Scott is term-limited. There are lists of declared and potential candidates, and even some early polling results.