This is definitely a hard question to answer and I have been struggling with it myself. It can feel like a monumental effort when it feels like you are one person doing it. It does feel like the tide is turning though as issues like single-payer become more prevalent. I would say seek out more sophisticated associations/efforts that promote the issues you are passionate about and make sure they don't have a problem staying afloat, by contributing time or (more importantly) money to them. That might be a more effective way to support your cause.