Persuasion is a three pronged fork. You must demonstrate personal benefit, a dramatic difference, and a reason to believe. So, you must understand what motivates your donors, how you are not just better but different from other options, and you must build trust. You can't look at donors as a one-time transaction. Building relationships with donors requires a continuous effort and the ability to satisfy them as their interests shift.
Generally I recommend that anyone considering creating a charity because they like the cause should not start a charity. Instead they should figure out a way to make a lot of money and just give that money to an established charity. Running yet another charity when a similar one exists means that both starve and the cause loses. If you just make a lot of money and give it to the existing charity, you can steer them more towards the elements you personally care about. It's a lot easier than running your own charity.