For the first $200, you get 16% tax credit from Federal side, then any amount above $200, you can get 29% tax credit, which falls into the highest tax bracket. But since it's a tax credit, the refund is only paid up to your tax payable. But you can carry forward it.
If you're asking about the donation from which a capital gain incurred, you should be careful because CRA keep on rejecting some of such donations every year. Go to CRA's website and you'll find more.