Property can be legitimately gained in two ways, by homesteading it or earning it through a legitimate contract. When you homestead property, you find unused property and use it in a gainful way. In a new country, individual settlers will find plots of land to homestead and that will be their land to use. We rent or buy property from someone, we agree to work for a certain number of hours for a certain amount of money, we agree to pay a certain amount of money for a certain good or by our own choice we freely give our property to someone else. Of course it is, but we can only do so much and ultimately the only thing we are truly required to do is to be fair and just.
Social causes are a good example.
There are at least a million important causes out there. The whales need to be saved, woodlands need to be saved, women need equal rights, gays and lesbians need equal rights, racism needs to be ended, and more. It's easy to get wrapped up in lots of different causes, but we can only meaningfully contribute to so many causes. If you pick one, you can do a lot of good, you can spend your life organizing, protesting and working for that cause. If you pick two or three, you can do a bit for each.