The most effective phone calls take less than a minute: say your name, your city or ZIP code, and what you support/oppose, maybe a sentence on why. You’ll be marked down on a spread sheet that is discussed at the daily office strategy meeting.
Other actions like brief emails, meeting in-person at the district office, meeting in-person at the DC office, can also be effective, but take more time and energy. Emails aren’t always read right away like a phone call must be answered for example. And you generally need to make an appointment for an in-person meeting.
It’s highly variable, and yes I absolutely agree money in politics is a big problem. I do have a direct experience where reaching out to my Senators led to them aggressively and successfully opposing a provision in a law that would have had a big impact on me. Don’t want to dox myself, but this real change to a bill made a huge difference to me and many others. So it is possible to make an impact.