In the event this is a first offense, it is possible that you may be entitled to a non conviction program called ARD. If you complete the program the charges would be dismissed and you could have your record wiped clean. You may also have a defense to the case so you need to speak with a lawyer immediately.
ARD is certainly a possibility. The punishment really depends largely upon two things. How old was the individual that the alcohol was purchased for and what is the prior record of the offender. If the alcohol was purchased for someone18,19 or 20---that is much different than purchasing it for a 15 or 16 year old. Hire an attorney to assist in this matter.