Giving back to society means a very different thing to billionaires than it does to ordinary folk. They’d rather spend it on politicians to tear down the society they think is wrong rather than shore up the parts that are failing. I have always blamed the idea that seems to stem from liberal economics (not liberal in the American sense) that equates money with virtue, something that conservatives have taken on as a mantra.
So be careful what you wish for. Ordinary morality or virtue loses all meaning when the world becomes abstract due to your wealth.
Under my idea, spending on lobbying would affect the equation zero. Contribute to charity (which is still a wide range, Dolly Parton has done so much good through her works through self-initiated foundation that I would suggest she is the gold standard).
Give to existing charity. Create your own foundation (although our government should be watching like a hawk in such a scenario to make sure you're not just funneling money back to yourself).
There might be use in considering corporations "people". But that analogy only holds so far before it becomes worse than the disease it's trying to contain.
So be careful what you wish for. Ordinary morality or virtue loses all meaning when the world becomes abstract due to your wealth.