Possession of an ounce or less of marijuana in the state of Georgia is a misdemeanor, with a maximum possible penalty of a year in jail and/or a fine of up to $1,000. As you only got a citation, I assume that this is a first arrest. Otherwise, you'd likely have been taken into custody.
Though jail is possible, it is extremely unlikely. So long as you appear in court when scheduled, you should be able to resolve this matter without having to serve any time. You would be eligible for probation, for example, and Georgia has a special program allowing your conviction to be dismissed after successful completion of your supervision, which would include fines, community service, drug testing, and drug counseling or classes.
Your first court date is generally the arraignment, where your charges are formally read into the court record and you're asked how you plead. You need to plead not guilty, which you can do legally under US law, even if you know you had the marijuana. All criminal defendants are presumed innocent under US law and remain so until proved guilty beyond a reasonable doubt.
A not guilty plea allows you the time to get advised by a lawyer, to have him negotiate a plea agreement or to fight the case all the way to trial. Any other plea immediately will convict you, and once that happens you cannot negotiate anything further on your behalf.
As I indicated, you shouldn't have to worry at all about jail. What's more concerning is keeping a drug conviction off of your criminal history. On a first arrest you'd be eligible for a diversion type of disposition, which is what I mentioned to you before. While you are eligible for it, however, it may have to be negotiated for you. For that reasons and all of the other reasons I have discussed above, it is best to leave your defense to a criminal lawyer.
If you can afford one, have him with you in court at your arraignment. If you are indigent and can't afford a lawyer without suffering severe economic hardship, you'd be eligible for a free lawyer. In that case, once you plead not guilty, you can tell the judge that you are unable to afford representation and ask him to appoint you a public defender. He will put the case over for a new date for your lawyer to appear and assist you.