All the nonrefundable credits are added together (on Form 1040 line 21), and the total cannot exceed the tax on Form 1040 line 18. So there is really no order to which credits you get. It just depends on the total.
Donations, mortgage interest, and real estate tax are not credits. They are itemized deductions. They do not directly affect your credits. The itemized deductions might reduce your taxable income, so they could reduce the amount of taxable income, thereby indirectly reducing the total amount of nonrefundable credits that you will get.
