If you are able to itemize you just get a percentage of your deductions back. Like if you are in the 25% tax bracket for a $100 deduction you will save $25. It isn't added on to your refund. Deductions reduce your income so you get taxed on a lower amount.
And that is just for the amount that puts you over the Standard Deduction. Now that the Standard Deduction is higher many people will be switching to the Standard Deduction. And there is a max 10,000 limit (5,000 MFS) of property tax and state taxes "SALT". And you can only deduct Medical that’s over 10% of your AGI.
For 2019 the standard deduction amounts are:
Single 12,200 + 1,650 for 65 and over or blind
HOH 18,350 + 1,650 for 65 and over or blind
Joint 24,400+ 1,300 for each 65 and over or blind
Married filing Separate 12,200 + 1,300 for 65 and over or blind
