I live in GA and I was arrested for taking 1800 dollars in cash,gift cards. No I didn't do it. What should be my next step.

Run to mexico ? OK, seriously, get an attorney, that is the only thing you can do. You have been arrested which means you are charged, I will assume you were arrested, had your first appearance and made bail ( since you are not in jail sending this)

So what is the actual charge, robbery, theft by taking, forgery??
The issue is the DA has to make the exact charge by showing evidence that the judge or jury will accept as proof. So your attorney will ask for a copy of all the evidence and review what they have. And as silly as it sounds, just being not guilty is not always enough, if they have evidence that makes you look guilty. Were you in control of the money that is missing ?

Also if you were aware or had knowledge of the crime or helped plan it, even if you did not do it, in GA you may still be charged as a party to the crime.

Do they have you on some kind of video tape that shows otherwise? How are they going to prove you are the thief? I sure hope that they have good evidence for their case.