"What can I do besides going to a bunch of protests and wearing a funny suit?"
You organize.
You unionize your workplace.
You get to know your neighbors and watch out for each other.
You volunteer and feed the hungry.
You pay your land tax to native folks. (For SF Bay Area Ohlone lands: https://sogoreate-landtrust.org/shuumi-land-tax/)
You help radical politicians in local campaigns, or run for them yourself.
You build open source software that helps sex workers (hi).
You democratize at the ground level, in any way you can manage.
You don't need a fucking armed revolution for any of this. There's so much you can do. You don't have to do all of it, and that's the beauty of it all: We all just need to pick one or a couple of things we care strongly about, and find others that feel the same, and focus on that. When we're all doing little things, it adds up to very big things.
That's your answer.
I don't really care much either way about the No Kings thing. I think if it inspires folks, that's great, but I also know The Powers That Be don't feel much besides mild embarrassment about it. You want to change shit, you actually need to mobilize into tangible action, not just carry around a little sign once a year and call it a day.