When you've been charged with any type of crime it's always recommended that you at least consult with an attorney to find out your options. Assuming that you can argue your own case or assuming that as a first-time offender you'll be shown leniency can be very shortsighted and costly. Consider why that is and how a good criminal defense lawyer can help you, no matter the charge.
1. Even first-time offenders can face jail time
Very often a first-time offender may be shown some leniency and this can certainly be asked for when brought before a judge, but this isn't always a guarantee. Some crimes come with recommendations for jail time and some judges want to make examples out of defendants, even if this is their first time in court. Assuming that you can simply point out that it's your first offense and will be given probation can be a costly mistake.
2. First-time offenses can mean hefty fines and a permanent criminal record
Even if you avoid jail time, a first-time offense can mean very heavy fines and a criminal record. The fines may be more than you can pay and an attorney can argue to get these reduced, based on your income and employment.
A criminal defense attorney can also argue to get your charges themselves reduced, so that the criminal record you have isn't so damaging to you in the long run. For example, a drunk and disorderly charge might be reduced to a loitering charge, or being caught with a marijuana cigarette can be reduced to simply possessing drug paraphernalia. These types of charges may not seem so serious to anyone who accesses your criminal record in the future, such as prospective employers or banks and other lenders.
3. Alternative sentencing may be available to you
Rather than jail time, a good criminal defense attorney may be able to argue for alternative sentencing. This can mean community service, rehabilitation programs, time spent in a halfway house, and the like. These can be a better choice for you than spending time in jail, but very often a prosecutor won't automatically offer them to defendants even for their first offense.
Your attorney will know if these are options and will know how to ask about them and argue for them in your case. This can keep you out of jail while still keeping the court satisfied that you're being suitably punished, which is often what they want even for first-time offenders.