Wouldn't a good start be to have representative democracy in the US? If you only have two big parties, then you will need huge marketing to get to the top of one of those. And that money seems to come from big lobbyists most of the time.
In the Nordic countries of Europe they have several smaller parties who need to go together to form a government.
It's not always pretty, but it generally means that the minorities get heard a lot more than in British inspired two-party 'democracies'.
What do you think? Or are all forms of government too vulnerable to corruption?
Yes.
Inherently so because they seek to govern and rule people --- not to actually serve them.
I have a lot of experience in this area.