I am 66 years old, married home owner, 8 year old dependent child. What discounts do I get when i file my 2018 taxes?

Discounts?  Do you mean what can you enter on your tax return?  If you are filing a joint return--which is almost always best--then your standard deduction will be $24,000 + $1300 for each spouse 65 or older.  You have not indicated what your source of income is, so we cannot comment on whether you qualify to get the child tax credit, earned income credit, or childcare credit.  If you are a homeowner then you might be able to deduct mortgage interest, property taxes paid or loan origination points paid in 2018--but again--we do not know anything about your income or if you are having tax withheld from your income.

Using itemized deductions will be harder this year for many people since the standard deduction is so high.  If your itemized deductions do not exceed your standard deduction, then they will not affect your tax due or refund.  

You should just begin a tax return and enter all of your personal information, including your dependent child with the child's Social Security number, and all of your income, then go to the deductions and credit section to see what you have to enter.